Method for fabricating solid oxide fuel cell module

ABSTRACT

There is provided a method of manufacturing a solid oxide fuel cell module comprising a plurality of cells each made up of a fuel electrode, an electrolyte, and an air electrode sequentially formed on a surface of a substrate with an internal fuel flow part provided therein, at least a face of the substrate, in contact with the cells, and interconnectors, being an insulator, and the cells adjacent to each other, being electrically connected in series through the intermediary of the respective interconnectors, said method of manufacturing the solid oxide fuel cell module comprising the steps of co-sintering the respective fuel electrodes, and the respective electrolytes, subsequently forming a dense interconnector out of a dense interconnector material, or an interconnector material turning dense by sintering in at least parts of the solid oxide fuel cell module, in contact with the respective fuel electrodes, and the respective electrolyte, and forming an air electrode on the respective electrolytes before electrically connecting the air electrode with the respective dense interconnectors. With the invention, it is possible to solve various problems of sinterability, encountered in the process of manufacturing the solid oxide fuel cell module of a multi-segment type, and to secure electrical contact of the parts of the respective dense interconnectors, in contact with the fuel electrodes while attaining high gas-sealing performance by the agency of the respective dense interconnectors, and electrolytes, thereby enhancing productivity.

TECHNICAL FIELD

The invention relates to a method of manufacturing a solid oxide fuelcell module, and more specifically, to a method of manufacturing a solidoxide fuel cell module of a multi-segment type.

BACKGROUND TECHNOLOGY

A solid oxide fuel cell (referred to hereinafter merely as an SOFC whereappropriate) is a fuel cell using an oxide as a solid electrolyticmaterial having ionic conductivity. The fuel cell generally has anoperating temperature as high as on the order of 1000° C., but there haslately been developed one having an operating temperature not higherthan 800° C., for example, on the order of 750° C. With the SOFC, thereare disposed a fuel electrode (that is, an anode), and an air electrode(that is, a cathode) with an electrolytic material sandwichedtherebetween, thereby making up a single cell as a three-layer unit ofthe fuel electrode/an electrolyte/the air electrode. Although the airelectrode is an oxygen electrode in the case of using oxygen as anoxidizing agent, it includes the oxygen electrode according to theinvention.

When the SOFC is operated, fuel is fed to the fuel electrode side of thesingle cell (also referred to merely as “a cell” where appropriate inthe present description), air and oxygen enriched air as an oxidizingagent or oxygen is fed to the air electrode side thereof, and electricpower is obtained by connecting both the electrodes to an external load.However, with the single cell of one unit only, a voltage only on theorder of 0.7V at most can be obtained, so that there is the need forconnecting in series a plurality of the single cells together in orderto obtain electric power for practical use. For the purpose ofelectrically connecting adjacent cells with each other whilesimultaneously feeding fuel, and air to the fuel electrode, and the airelectrode, respectively, after properly distributing them, andsubsequently, effecting emission thereof, separators (=interconnectors)and the single cells are alternately deposited.

Such a SOFC module is a type wherein a plurality of the single cells arestacked one on top of another, but it is conceivable to adopt amulti-segment type in place of such a type as described. For example, inFifth European Solid Oxide Fuel Cell forum (1 to 5, Jul., 2002) p.1075-, the external appearance, and so forth, of the multi-segment typeare disclosed although the contents thereof are not necessarilyclear-cut in detail. As the multi-segment type, two types including acylindrical type, and a hollow flat type are conceivable.

FIGS. 1(a) to 1(c) are views showing an example of the structure of thehollow flat type of the two types, FIG. 1(a) being an obliqueperspective view, FIG. 1(b) a plan view, and FIG. 1(c) a sectional viewtaken on line A-A in FIG. 1(b). As shown in FIGS. 1(a) to 1(c), thereare formed a plurality of cells 2 each made up by stacking a fuelelectrode 3, an electrolyte 4, and an air electrode 5 in that order onan insulator substrate 1 in a hollow flat sectional shape, and therespective cells 2 are structured so as to be electrically connected inseries with each other through the intermediary of an interconnector 6,respectively. Fuel is caused to flow in space (=a hollow area) withinthe insulator substrate 1, that is, an internal fuel flow part 7, inparallel with a lineup of the cells 2, as indicated by an arrow (→) inFIGS. 1(a), and 1(c). In FIG. 1(c), the interconnector 6 is seencovering part of the surface of the air electrode 5, however, may coverthe entire surface thereof. In this respect, the same can be saidhereinafter.

For a constituent material of the insulator substrate in the hollow flatsectional shape, use can be made of a porous material capable ofwithstanding the operating temperature of an SOFC module, but use isnormally made of ceramics. For use in the electrolyte, a solidelectrolytic material having ionic conductivity is sufficient, and usecan be of a sheet like sintered body such as, for example, yttriastabilized zirconia (YSZ). For the fuel electrode, use is made of aporous material such as, for example, a mixture of Ni and yttriastabilized zirconia YSZ (Ni/YSZ cermet), and so forth. For the airelectrode, use is made of a porous material, for example, Sr dopedLaMnO₃, and so forth.

In fabrication of the respective cells, the fuel electrode, theelectrolyte, and the air electrode are normally fabricated by separateprocesses by screen printing, and so forth, and those electrodes aredeposited in that order on top of the insulator substrate in the hollowflat sectional shape to be subsequently sintered, thereby forming therespective cells. The respective adjacent cells are structured so as tobe electrically connected in series with each other through theintermediary of the interconnector.

DISCLOSURE OF THE INVENTION

However, at the time of manufacturing the SOFC module of themulti-segment type, that is, the SOFC module in which the respectivecells are lined up as described in the foregoing, in the case of using,for example, the Ni/YSZ cermet as the constituent material of the fuelelectrode, if the insulator substrate, and the respective fuelelectrodes, being in contact with each other, are sintered, theconstituent material of the fuel electrodes undergoes contraction.Meanwhile, because the insulator substrate does not undergo thermalcontraction, the fuel electrodes are cracked. For this reason, infabrication of the cells, production yield is poor and productivity islow. In addition there has also arisen a problem that mechanicalstrength of the fuel electrodes is very weak.

With the SOFC module of the multi-segment type, there is the need forelectrically connecting the fuel electrode to the air electrode betweenthe adjacent cells through the intermediary of an interconnector. Withthe interconnectors, it is required that electrical resistivity is low,and contact resistance can be controlled, and furthermore, high sealingperformance and high heat resistance are required at both sides of thefuel electrode and the air electrode. In addition, chemical stability isrequired in both an oxidizing atmosphere, and a reducing atmosphere. Forthose reasons, as the constituent material of the interconnector, (La,Sr) CrO₃ has been used in the past.

However, although this material, that is, (La, Sr) CrO₃ has highchemical stability in both the oxidizing atmosphere, and reducingatmosphere, it has been very difficult to obtain a dense sintered bodyout of the material, thereby obtaining high gas-sealing performance.That is, since the material has poor sinterability, it has beendifficult to implement fabrication of the interconnector out of the samewith ease, and consequently, it has been impossible to securegas-sealing performance. Furthermore, because the material is high inelectrical resistivity, use thereof has been under constraints such asthe need for use after reduction in thickness thereof, or the need foruse at a high temperature around 1000° C.

It is therefore an object of the invention to provide a method ofmanufacturing a solid oxide fuel cell module of a multi-segment type,developed by solving various problems encountered in the process ofmanufacturing the solid oxide fuel cell module of the multi-segmenttype. More particularly, the object of the invention is to solveproblems of sinterability occurring between respective fuel electrodes,and respective electrolytes, among the respective fuel electrodes, therespective electrolytes, and respective interconnectors, among asubstrate, the respective fuel electrodes, and the respectiveelectrolytes, or among the substrate, the respective fuel electrodes,the respective electrolytes, and the respective interconnectors, and soforth, and further, to provide the method of manufacturing the solidoxide fuel cell module of the multi-segment type, capable of attaininghigh gas-sealing performance, enhancing productivity, and achievingreduction in cost.

The method of manufacturing the solid oxide fuel cell module, accordingto the invention, and variations thereof are sequentially describedhereinafter.

It is a first aspect of the invention to provide the method ofmanufacturing a solid oxide fuel cell module comprising a plurality ofcells each made up of a fuel electrode, an electrolyte, and an airelectrode sequentially formed on a surface of a substrate with aninternal fuel flow part provided therein, at least a face of thesubstrate, in contact with the cells, and interconnectors, being aninsulator, and the cells adjacent to each other, being electricallyconnected in series through the intermediary of the respectiveinterconnectors, said method of manufacturing the solid oxide fuel cellmodule comprising the steps of co-sintering the respective fuelelectrodes, and the respective electrolytes, subsequently forming adense interconnector out of a dense interconnector material, or aninterconnector material turning dense by sintering in at least parts ofthe solid oxide fuel cell module, in contact with the respective fuelelectrodes, and the respective electrolyte, and forming an air electrodeon the respective electrolytes before electrically connecting the airelectrode with the respective dense interconnectors.

It is a second aspect of the invention to provide the method ofmanufacturing a solid oxide fuel cell module comprising a plurality ofcells each made up of a fuel electrode, an electrolyte, and an airelectrode sequentially formed on a surface of a substrate with aninternal fuel flow part provided therein, at least a face of thesubstrate, in contact with the cells, and interconnectors, being aninsulator, and the cells adjacent to each other, being electricallyconnected in series through the intermediary of the respectiveinterconnectors, said method of manufacturing the solid oxide fuel cellmodule comprising the steps of co-sintering the substrate, therespective fuel electrodes, and the respective electrolytes,subsequently forming a dense interconnector out of a denseinterconnector material, or an interconnector material turning dense bysintering in at least parts of the solid oxide fuel cell module, incontact with the respective fuel electrodes, and the respectiveelectrolytes, and forming an air electrode on the respectiveelectrolytes before electrically connecting the air electrode with therespective dense interconnectors.

It is a third aspect of the invention to provide the method ofmanufacturing a solid oxide fuel cell module comprising a plurality ofcells each made up of a fuel electrode, an electrolyte, and an airelectrode sequentially formed on a surface of a substrate with aninternal fuel flow part provided therein, at least a face of thesubstrate, in contact with the cells, and interconnectors, being aninsulator, and the cells adjacent to each other, being electricallyconnected in series through the intermediary of the respectiveinterconnectors, said method of manufacturing the solid oxide fuel cellmodule comprising the steps of co-sintering the respective fuelelectrodes, the respective electrolytes, and a dense interconnectormaterial, or an interconnector material turning dense by co-sintering,in at least parts of the solid oxide fuel cell module, in contact withthe respective fuel electrodes, and the respective electrolytes, andforming an air electrode on the respective electrolytes beforeelectrically connecting the air electrode with the respective denseinterconnectors.

It is a fourth aspect of the invention to provide the method ofmanufacturing a solid oxide fuel cell module comprising a plurality ofcells each made up of a fuel electrode, an electrolyte, and an airelectrode sequentially formed on a surface of a substrate with aninternal fuel flow part provided therein, at least a face of thesubstrate, in contact with the cells, and interconnectors, being aninsulator, and the cells adjacent to each other, being electricallyconnected in series through the intermediary of the respectiveinterconnectors, said method of manufacturing the solid oxide fuel cellmodule comprising the steps of co-sintering the substrate, therespective fuel electrodes, the respective electrolytes, and a denseinterconnector material, or an interconnector material turning dense byco-sintering, in at least parts of the solid oxide fuel cell module, incontact with the respective fuel electrodes, and the respectiveelectrolytes, and forming an air electrode on the respectiveelectrolytes before electrically connecting the air electrode with therespective dense interconnectors.

It is a fifth aspect of the invention to provide the method ofmanufacturing a solid oxide fuel cell module comprising a plurality ofcells each made up of a fuel electrode, an electrolyte, and an airelectrode sequentially formed on a surface of a substrate with aninternal fuel flow part provided therein, at least a face of thesubstrate, in contact with the cells, and interconnectors, being aninsulator, and the cells adjacent to each other, being electricallyconnected in series through the intermediary of the respectiveinterconnectors, said method of manufacturing the solid oxide fuel cellmodule comprising the steps of disposing a dense interconnectormaterial, or an interconnector material turning dense by co-sintering,in portions of the respective fuel electrodes, subsequently covering therespective fuel electrodes, and the dense interconnector material, orthe interconnector material turning dense by co-sintering beforeco-sintering the respective fuel electrodes, the dense interconnectormaterial, or the interconnector material turning dense by co-sintering,and the respective electrolytes, thereby forming dense interconnectors,forming an air electrode on the respective electrolytes, andsubsequently electrically connecting the air electrode with therespective dense interconnectors.

It is a sixth aspect of the invention to provide the method ofmanufacturing a solid oxide fuel cell module comprising a plurality ofcells each made up of a fuel electrode, an electrolyte, and an airelectrode sequentially formed on a surface of a substrate with aninternal fuel flow part provided therein, at least a face of thesubstrate, in contact with the cells, and interconnectors, being aninsulator, and the cells adjacent to each other, being electricallyconnected in series through the intermediary of the respectiveinterconnectors, said method of manufacturing the solid oxide fuel cellmodule comprising the steps of disposing a dense interconnectormaterial, or an interconnector material turning dense by co-sintering,in portions of the respective fuel electrodes, subsequently covering therespective fuel electrodes, and the dense interconnector material, orthe interconnector material turning dense by co-sintering beforeco-sintering the substrate, the respective fuel electrodes, the denseinterconnector material, or the interconnector material turning dense byco-sintering, and the respective electrolytes, thereby forming denseinterconnectors, forming an air electrode on the respectiveelectrolytes, and subsequently electrically connecting the air electrodewith the respective dense interconnectors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) to 1(c) are views showing an example of the structure of ahollow flat type solid oxide fuel cell module;

FIGS. 2(a) to 2(e), and FIGS. 3(a) to 3(b) are views showing examples ofthe structure according to this invention of “a substrate with aninternal fuel flow part provided therein, at least a face thereof, incontact with cells, and interconnectors, being an insulator”;

FIGS. 4(a) to 4(c) are views showing other examples of the structureaccording to this invention of “a substrate with an internal fuel flowpart provided therein, at least a faces thereof, in contact with cells,and interconnectors, being an insulator”;

FIGS. 5(a) and 5(b) are views showing still other examples of thestructure according to this invention of “a substrate with an internalfuel flow part provided therein, at least a faces thereof, in contactwith cells, and interconnectors, being an insulator”;

FIGS. 6(a) to 6(c) are views showing another example of an SOFC modulestructure according to the invention;

FIGS. 7(a) to 7(c) are views showing several examples of modes ofstructure, in which cells disposed in respective rows of an SOFC moduleare varied in cell area along the direction of fuel flow, by the row,respectively;

FIGS. 8(a), 8(b) and FIGS. 9(a), 9(b) are views showing several examplesof modes of structure, in which cells disposed in respective rows of anSOFC module are varied in cell area along the direction of fuel flow, bythe row, on the basis of an SOFC sub-module unit, respectively;

FIG. 10 is a view showing an interconnector configuration construction 1according to the invention;

FIG. 11 is a view showing an interconnector configuration construction 2according to the invention;

FIG. 12 is a view showing an interconnector configuration construction 3according to the invention;

FIG. 13 is a view showing an interconnector configuration construction 4according to the invention;

FIG. 14 is a view showing the interconnector configuration construction5 according to the invention;

FIG. 15 is a view showing the interconnector configuration construction6 according to the invention;

FIG. 16 is a view showing the interconnector configuration construction7 according to the invention;

FIG. 17 is a view showing the interconnector configuration construction8 according to the invention;

FIG. 18 is a view showing the interconnector configuration construction9 according to the invention;

FIG. 19 is a view showing the interconnector configuration construction10 according to the invention;

FIG. 20 is a view showing the interconnector configuration construction11 according to the invention;

FIG. 21 is a view broadly showing a method of manufacturing an SOFCmodule according to Working Example 1 of the invention;

FIGS. 22(a) to 22(c) are views broadly showing the SOFC modulemanufactured by Working Example 1; and

FIG. 23 is a view broadly showing a method of manufacturing an SOFCmodule according to Working Example 2 of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is concerned with a method of manufacturing anSOFC module comprising a plurality of cells each made up of a fuelelectrode, an electrolyte, and an air electrode sequentially formed on asurface of a substrate with an internal fuel flow part provided therein,at least a face of the substrate, in contact with the cells, andinterconnectors, being an insulator, (that is, the cells each providedwith the fuel electrode, electrolyte, and air electrode, sequentiallyformed on the surface of the substrate thereof), and the cells adjacentto each other, being electrically connected in series through theintermediary of the respective interconnectors. Herein, theinterconnector refers to a member linking the fuel electrode of one ofthe adjacent cells, that is, the preceding cell, with the air electrodeof the other cell, that is, the cell immediately succeeding thereto.

The invention has a fundamental feature in that prior to formation ofthe air electrode on the respective electrolytes, (a) the respectivefuel electrodes, and the respective electrolytes are co-sintered, (b)the substrate, the respective fuel electrodes, and the respectiveelectrolytes are co-sintered, or (c) those members, and at leastportions of an interconnector material, in contact with the respectivefuel electrodes, and the respective electrolytes, are co-sintered. Thecase of co-sintering under (c) as above include a case of the respectivefuel electrodes, and the respective electrolytes being sinteredsimultaneously with the portions of the interconnector material, incontact with at least the respective fuel electrodes, and the respectiveelectrolytes, and a case of the substrate, the respective fuelelectrodes, and the respective electrolytes being sinteredsimultaneously with the portions of the interconnector material, incontact with at least the respective fuel electrodes, and the respectiveelectrolytes.

That is, in terms of combination of members co-sintered in co-sinteringunder (a) to (c) as above, sintering is made between the respective fuelelectrodes, and the respective electrolytes (i), among the substrate,the respective fuel electrodes, and the respective electrolytes (ii),among the respective fuel electrodes, the respective electrolytes, andthe portions of the interconnector material, in contact with at leastthe respective fuel electrodes, and the respective electrolytes (iii),and among the substrate, the respective fuel electrodes, the respectiveelectrolytes, and the portions of the interconnector material, incontact with at least the respective fuel electrodes, and the respectiveelectrolytes (iv). A co-sintered body is formed between the respectivemembers described. A sintering temperature is in a range of 800 to 1600°C., preferably a range of 1200 to 1500° C., and is suitably selectedbefore application, depending on the kinds of constituent materials ofthe respective members, combination of the respective members, and soforth.

Fundamental Features of the Invention (1) to (6)

The invention (1) has a feature in that prior to formation of an airelectrode on respective electrolytes, respective fuel electrodes, andthe respective electrolytes are co-sintered, and a dense interconnectoris formed out of a dense interconnector material, or an interconnectormaterial turning dense by sintering, in at least parts of the solidoxide fuel cell module, in contact with the respective fuel electrodes,and the respective electrolytes. The dense interconnector formed at thispoint in time is not electrically connected to the respective airelectrodes as yet, and accordingly, corresponds to a precursory memberin the process of forming the interconnector as a constituent element ofthe cell. With the invention (1), a co-sintered body of the fuelelectrodes, and the electrolytes is separately joined to a substratethrough the intermediary of a jointing material, and so forth.

The invention (2) has a feature in that prior to formation of an airelectrode on respective electrolytes, a substrate, respective fuelelectrodes, and the respective electrolytes are co-sintered, and atleast portions of a dense interconnector, coming into contact with boththe respective fuel electrodes, and the respective electrolytes, areformed of a dense interconnector material, or an interconnector materialturning dense by sintering. The dense interconnector formed at thispoint in time is not electrically connected to the respective airelectrodes as yet, and accordingly, corresponds to a precursory memberin the process of forming the interconnector as a constituent element ofthe cell.

The invention (3) has a feature in that prior to formation of an airelectrode on respective electrolytes, respective fuel electrodes, therespective electrolytes, and at least portions of a dense interconnectormaterial, or portions of an interconnector material turning dense byco-sintering, coming into contact with both the respective fuelelectrodes, and the respective electrolytes, are co-sintered. At thispoint in time, the dense interconnector material is turned into a denseinterconnector by co-sintering, and the interconnector material turningdense by co-sintering is turned into a dense interconnector by theco-sintering, however, the dense interconnector formed at this point intime is not electrically connected to the respective air electrodes in astage of the co-sintering, and accordingly, corresponds to a precursorymember in the process of forming the interconnector as a constituentelement of the cell. With the invention (3), respective co-sinteredbodies are separately jointed to a substrate through the intermediary ofa jointing material, and so forth.

The invention (4) has a feature in that prior to formation of an airelectrode on respective electrolytes, a substrate, respective fuelelectrodes, the respective electrolytes, and at least portions of adense interconnector material, or portions of an interconnector materialturning dense by co-sintering, coming into contact with both therespective fuel electrodes, and the respective electrolytes, areco-sintered. At this point in time, the dense interconnector material isturned into a dense interconnector by the co-sintering, and theinterconnector material turning dense by the co-sintering is turned intoa dense interconnector by the co-sintering, however, the denseinterconnector formed at this point in time is not electricallyconnected to the respective air electrodes in a stage of theco-sintering, and accordingly, corresponds to a precursory member in theprocess of forming the interconnector as a constituent element of thecell.

The invention (5) has a feature in that prior to formation of an airelectrode on respective electrolytes, a dense interconnector material,or an interconnector material turning dense by co-sintering is disposedon portions of respective fuel electrodes, and the respective fuelelectrodes, and the interconnector material are subsequently coveredwith the respective electrolytes before the respective fuel electrodes,the interconnector material, and the respective electrolytes areco-sintered. At this point in time, the dense interconnector material isturned into a dense interconnector by the co-sintering, and theinterconnector material turning dense by the co-sintering is turned intoa dense interconnector by the co-sintering, however, the denseinterconnector formed at this point in time is not electricallyconnected to the respective air electrodes in a stage of theco-sintering, and accordingly, corresponds to a precursory member in theprocess of forming the interconnector as a constituent element of thecell. With the invention (5), respective co-sintered bodies areseparately jointed to a substrate through the intermediary of a jointingmaterial, and so forth.

The invention (6) has a feature in that prior to formation of an airelectrode on respective electrolytes, a dense interconnector material,or an interconnector material turning dense by co-sintering is disposedon portions of respective fuel electrodes, and a substrate, therespective fuel electrodes, and the interconnector material aresubsequently covered with the respective electrolytes before thesubstrate, the respective fuel electrodes, the interconnector material,and the respective electrolytes are co-sintered. At this point in time,the dense interconnector material is turned into a dense interconnectorby the co-sintering, and the interconnector material turning dense bythe co-sintering is turned into a dense interconnector by theco-sintering, however, the dense interconnector formed at this point intime is not electrically connected to the respective air electrodes in astage of the co-sintering, and accordingly, corresponds to a precursorymember in the process of forming the interconnector as a constituentelement of the cell.

With the invention, as a constituent material of “a substrate with aninternal fuel flow part provided therein, at least a face thereof, incontact with cells, and interconnectors, being an insulator”, use can bemade of a mixture of MgO, and MgAl₂O₄, a zirconia based oxide, a mixtureof the zirconia based oxide, MgO, and MgAl₂O₄, and so forth. Among thosematerials, the mixture of MgO, and MgAl₂O₄ is preferably a mixture ofMgO, and MgAl₂O_(4,) containing 20 to 70 vol. % of MgO. Further, as anexample of the zirconia based oxide, there can be cited an yttriastabilized zirconia [YSZ: (Y₂O₃)_(x)(ZrO₂)_(1-x) (in chemical formula,x=0.03 to 0.12)], and so forth.

As a constituent material of the fuel electrode, use is made of materialcomposed mainly of Ni, and a ceramic material containing a metal. As theceramic material of the ceramic material containing the metal, use ismade of, for example, an yttria stabilized zirconia [YSZ:(Y₂O₃)_(x)(ZrO₂)_(1-x) (in chemical formula, x=0.05 to 0.15)], and asthe metal, use is made of at least one kind of metal, namely, one kindor not less than two kinds of metals selected from the group consistingof Ni, Cu, Fe, Ru, and Pd. Among those ceramic material containing themetals, YSZ containing Ni, that is, a mixture of Ni and YSZ[(Y₂O₃)_(x)(ZrO₂)_(1-x) (in chemical formula, x=0.05 to 0.15)] is apreferable material for the fuel electrode according to the invention,and particularly, the material with not less than 40 vol. % of Nidiffused in the mixture is preferably used.

As a constituent material of the electrolyte, use may be of a solidelectrolytic material having ionic conductivity, and as examples of theconstituent material, there can be included materials described underitems (1) to (4) given hereunder:

(1) an yttria stabilized zirconia [YSZ: (Y₂O₃)_(x)(ZrO₂)_(1-x) (inchemical formula, x=0.05 to 0.15)].

(2) a scandia stabilized zirconia [(Sc₂O₃)_(x)(ZrO₂)_(1-x) (in chemicalformula, x=0.05 to 0.15)].

(3) an yttria doped ceria [(Y₂O₃)_(x)(CeO₂)_(1-x) (in chemical formula,x=0.02 to 0.4)].

(4) a gadolinia doped ceria [(Gd₂O₃)_(x)(CeO₂)_(1-x) (in chemicalformula, x=0.02 to 0.4)].

Effect of the Invention

With an SOFC module of a multi-segment type, according to the invention,it is possible to solve problems of sinterability occurring between therespective fuel electrodes, and the respective electrolytes, among therespective fuel electrodes, the respective electrolytes, and therespective interconnectors, among the substrate, the respective fuelelectrodes, and the respective electrolytes, or among the substrate, therespective fuel electrodes, the respective electrolytes, and therespective interconnectors, and so forth, and further, to attain highgas-sealing performance by virtue of the respective denseinterconnectors, and the respective electrolytes, and secure electricalcontact at portions of the respective interconnectors, in contact withthe respective fuel electrodes. Consequently, it is possible to obtainvarious useful effects such as enhancement in productivity of the solidoxide fuel cell module of the multi-segment type, and capability ofachieving reduction in cost.

Constituent Material of the Interconnector

In the SOFC module, the interconnector linking the fuel electrode to theair electrode between the respective cells adjacent to each other isrequired to achieve electrical continuity between the fuel electrode andthe air electrode, and to be low in electrical resistance, having highgas-sealing performance, and heat resistance at both the fuel electrodeand the air electrode. With the invention, as a constituent material ofthe interconnector, use is made of material meeting those requirements,and as examples of the constituent material of the interconnector, therecan be cited materials described under items (1) to (4) given hereunder:

(1) a mixture of a glass and an electroconductive material. Since aglass is normally an insulator, in order to cause current to flowtherethrough, the surface thereof is provided with a metal such as Ag,Pt, and so forth, or a film of In₂O₈, or SnO₂, and so forth, forutilization of electroconductivity thereof. With the invention, as theconstituent material of the interconnector, use is made of the mixtureof the glass and the electroconductive material, that is, the mixturemade by mixing the electroconductive material into the glass. There isno particularly limitation to the kind of glass used in this case, anduse can be made of glass of a network structure, including SiO₂, orAl₂O₃ in addition to SiO₂, containing K₂O, ZnO, BaO, Na₂O, CaO, and soforth, and for example, among soda glass, borosilicate glass, silicaglass, and so forth, suitable one may be selected for use. Use ispreferably made of glass having properties of thermal expansioncoefficient in a range of 8.0 to 14.0×10⁻⁶ K⁻¹, and a softening point ina range of 600 to 1000° C. As the electroconductive material mixed intothe glass, use is made of a metal or an electroconductive oxide. As themetal, use is made of at least one kind of metal selected from the groupconsisting of Pt, Ag, Au, Ni, Co, W, and Pd, that is, metal containingone kind or not less than two kinds among those metals. As an example ofthe case of the metal containing not less than two kinds of thosemetals, there can be cited an alloy containing Ag, for example, an Ag—Pdbase alloy, and so forth. As an example of the electroconductive oxide,there can be cited (a) a perovskite type ceramics composed of not lessthan two elements selected from the group consisting of La, Cr, Y, Ce,Ca, Sr, Mg, Ba, Ni, Fe, Co, Mn, Ti, Nd, Pb, Bi, and Cu, (b) an oxideexpressed by chemical formula (Ln, M) CrO₃ (in the chemical formula, Lnrefers to lanthanoids, and M refers to Ba, Ca, Mg, or Sr), (c) an oxideexpressed by chemical formula M (Ti_(1-x) Nb_(x)) O₃ (in the chemicalformula, M refers to at least one element selected from the groupconsisting of Ba, Ca, Li, Pb, Bi, Cu, Sr, La, Mg, and Ce, x=0 to 0.4)and so forth.

Electroconductive material content of the mixture of the glass and theelectroconductive material is preferably not less than 30 vol. % of themixture, in which case, the interconnector can maintain excellentelectroconductivity. Further, it is preferable that the mixture of theglass and the electroconductive material is subjected to heat treatmentat not higher than the melting point of the electroconductive materialafter the mixture is applied between the fuel electrode of one ofadjacent cells, and the air electrode of the other cell.

(2) an oxide containing Ti, expressed by, for example, chemical formulaM (Ti_(1-x) Nb_(x)) O₃ (in the chemical formula, M refers to at leastone element selected from the group consisting of Ba, Ca, Li, Pb, Bi,Cu, Sr, La, Mg, and Ce, x=0 to 0.4)

(3) material composed mainly of Ag. In the case of this material, it isdesirable to cover an interconnector made of this material with glass.

(4) material composed of one substance or not less than two substances,selected from the group consisting of Ag, Ag solder, and a mixture of Agand glass.

As the Ag solder, use is made of a metal soldering material containingat least Ag. Examples thereof include an Ag—Cu alloy (for example,Ag=71.0 to 73.0%, Cu=balance; 780 to 900° C.) (% refers to wt. %,temperature ° C. refers to soldering temperature; the same applieshereinafter), an Ag—Cu—Zn alloy (for example, Ag=44.0 to 46.0%, Cu=29.0to 31.0%, Zn=23.0 to 27.0%; 745 to 845° C.), an Ag—Cu—Zn—Cd alloy (forexample, Ag=34.0 to 36.0%, Cu=25.0 to 27.0%, Zn=19.0 to 23.0%, Cd=17.0to 19.0%; 700 to 845° C.), an Ag—Cu—Zn—Sn alloy (for example, Ag=33.0 to35.0%, Cu=35.0 to 37.0%, Zn=25.0 to 29.0%, Sn=2.5 to 3.5%; 730 to 820°C.), an Ag—Cu—Zn—Ni alloy (for example, Ag=39.0 to 41.0%, Cu=29.0 to31.0%, Zn=26.0 to 30.0%, Ni=1.5 to 2.5%; 780 to 900° C.), and so forth.

There is no particularly limitation to an application form of the Agsolder, and the Ag solder can be used in the form of powders, slurry,sol, paste, sheet, or wire, and so forth. The slurry, sol, and paste canbe prepared by dispersing, for example, the Ag solder in powdery form,together with a binder, such as PVA, and so forth, into a solvent suchas water, an organic solvent, and so forth. The sheet, and wire can beprepared by, for example, rolling a lump of the Ag solder. Use of the Agsolder in the form of the slurry, sol, or paste renders operationadvantageous.

When constituting the interconnector linking the fuel electrode to theair electrode between the respective cells adjacent to each other by useof the above-described constituent material of the interconnector,better mechanical, and electrical joining can be implemented at portionsof the respective interconnectors, in contact with the fuel electrodes,and the electrolytes, by forming at least the portions thereof, incontact with the fuel electrodes, and the electrolytes, respectively,(that is, the portions of the interconnector, in contact with the fuelelectrode, and the electrolyte), or only those portions with the use ofmaterial composed of one kind or not less than two kinds of materialselected from the group consisting of the above-exemplified materials ofi) Ag, ii) the material composed mainly of Ag, iii) the Ag solder, iv)the mixture of Ag and the glass, and v) the electroconductive oxide.

There are described hereinafter fabrication methods corresponding tostructure, layout, and configuration, respectively, in sequence, forrespective constituent members, such as the substrate, cells,interconnectors, and forth, of the SOFC module as the target for themethod of manufacturing the SOFC module, according to the invention.

Construction of the SOFC Module as the Target for the ManufacturingMethod According to the Invention

Any SOFC module in which a multi-segment type cell layout is adopted canbe a target for the method of manufacturing the SOFC module, accordingto the invention. The SOFC module shown in FIG. 1 is an example of ahollow flat form, showing an external appearance, and the form andexternal appearance of the SOFC module of the multi-segment type aredependent mainly on a cross-sectional shape of the substrate thereof,and a length thereof, in the direction of fuel flow inside thesubstrate. Accordingly, with reference to the SOFC module as the targetfor the manufacturing method according to the invention, a structure ofthe substrate thereof is first described hereinafter.

Substrate Structure

As the substrate for the present invention, use is made of a substratewith an internal fuel flow part provided therein, at least a facethereof, in contact with cells, and interconnectors, being an insulator.More specifically, (1) the substrate is required to meet threerequirements, namely, the substrate to be structured so as to have theinternal fuel flow part therein, (2) the substrate to be structured soas to enable a plurality of cells to be disposed on the outer facesthereof, and (3) the substrate to be structured such that at least theface thereof, in contact with the cells, and interconnectors, is theinsulator, and it need only be sufficient that at least thoserequirements are met. The structure thereof can be polygonal(quadrilateral, flat rectangular, and so forth), tubular, elliptical,and of other suitable forms, in a cross-sectional shape. Besides thecase where one unit of the internal fuel flow part is provided insidethe substrate in any of those shapes, a plurality of units of theinternal fuel flow parts can be provided therein.

Example 1 of Substrate Structure

FIGS. 2(a) to 2(e) and FIGS. 3(a), 3(b) are views showing some examplesof a substrate structure. With any of the examples shown in FIGS. 2(a)to 2(e), and 3(a) and 3(b), there are formed a plurality of cells eachmade up of a fuel electrode 12, an electrolyte 13, and an air electrode14, stacked in sequence on top of an insulator substrate 11. Referencenumeral 15 denotes a hollow region, that is, the internal fuel flowpart. FIG. 2(a) shows an example of the insulator substratehollow-rectangular or hollow-flat, in cross-section, showing the case ofthe insulator substrate 11 provided with one hollow region. The hollowregion functions as a fuel flow path. FIGS. 2(b) to 2(e) are viewsshowing examples of the insulator substrate rectangular or flat, incross-section, respectively, showing the cases of the respectiveinsulator substrates provided with a plurality of hollow regions, thatis, a plurality of the fuel flow paths. FIGS. 2(b) and 2(c) are viewsshowing examples of the respective fuel flow paths being circular orelliptical, in cross-section, and FIGS. 2(d) and 2(e) are views showingexamples of the respective fuel flow paths being quadrilateral, orrectangular in cross-section. FIGS. 3(a) and 3(b) are views showingexamples of the insulator substrate circular or elliptical, incross-section, showing the cases of the respective insulator substratesbeing provided with a plurality of the fuel flow paths, FIG. 3(a) is aview showing an example of the respective fuel flow paths being circularor elliptical, in cross-section, and FIG. 3(b) is a view showing anexample of the respective fuel flow paths being quadrilateral, orrectangular in cross-section. The cross-sectional shapes of therespective fuel flow paths are not limited to forms shown in thosefigures, and may be triangular or other suitable shapes.

Example 2 of Substrate Structure

FIGS. 4(a) to 4(c) are views showing examples of the substratestructured so as to be quadrilateral or substantially quadrilateral incross-section, respectively. With an example shown in FIG. 4(a), a fuelelectrode 12 is disposed on both the upper side face, and the undersideface of an insulator substrate 11, and an electrolyte 13 is disposed onthe entire peripheral surface of the insulator substrate 11, includingthe fuel electrodes 12. Then, an air electrode 14 is disposed onportions of the surface of the fuel electrodes 12, corresponding to therespective fuel electrode 12, on the upper side, and underside. With theexample shown in FIG. 4(a), the fuel electrode, and the air electrodemay be disposed on both the right and left side faces of the insulatorsubstrate 11, as well. With an example shown in FIG. 4(b), a fuelelectrode 12 is disposed on the entire peripheral surface of aninsulator substrate 11, and an electrolyte 13 is disposed on the entireperipheral surface of the fuel electrode 12. Then, an air electrode 14is disposed on portions of the surface of the electrolyte 13, on theupper side, and underside, respectively. With an example shown in FIG.4(c), a fuel electrode 12 is disposed on the entire peripheral surfaceof an insulator substrate 11, and an electrolyte 13 is disposed on theentire peripheral surface of the fuel electrode 12. Then, an airelectrode 14 is disposed on portions of the surface of the electrolyte13, on the upper side, and underside, respectively, and a conductor oran air electrode is disposed on portions of the surface of theelectrolyte 13, other than the portions of the surface thereof, wherethe respective air electrodes 14 are disposed. In FIG. 4(c), theconductor or the air electrode that is disposed on the portions of thesurface of the electrolyte 13, other than the portions where therespective air electrodes 14 are disposed, is indicated by “16 (14)”.With the examples shown in FIGS. 4(b) and 4(c), the air electrode may bedisposed on both faces of the electrolyte 13, on the right and left sideof the fuel electrode, respectively, as well. In FIGS. 4(a) to 4(c),there are shown the cases of the substrate quadrilateral orsubstantially quadrilateral in cross-section, however, the same appliesto the cases of the substrate being in a shape other than that incross-section, such as other polygonal, elliptical, and so forth, incross-section. In other respects, the substrate is the same in structureas that shown in FIGS. 1(a) to 3(b).

Example 3 of Substrate Structure

As the substrate for the present invention, use is made of a substratewith an internal fuel flow part provided therein, at least a facethereof, in contact with cells, and interconnectors, being an insulator.FIGS. 5(a) and 5(b) are views showing examples of the structure of thesubstrate meeting such a requirement, in which at least the face of thesubstrate, in contact with the cells, is an insulator. As shown in FIG.5(a), portions of the substrate, in contact with respective fuelelectrodes 12, are made up of an insulator 11 while other portionthereof is made up of an electrically conductive substance 16. This isthe same as with the case where a face of the substrate, in contact withthe interconnector between respective cells adjacent to each other, isan insulator. With the example of the structure, shown in FIG. 5(b),there is shown the case where a substrate in whole, including the facesthereof, in contact with cells, respectively, is made up of theinsulator 11. In FIGS. 5(a) and 5(b), there are shown the cases of thesubstrate being in a shape rectangular or flat in cross-section,however, the same applies to the cases of the substrate being in a shapeother than that in cross-section, such as other shapes polygonal,elliptical, circular, and so forth, in cross-section, as described inExamples 1 and 2 of Substrate Structure (refer to FIGS. 2(a) to 4(c)).

Structure of Cells Disposed on a Substrate Face

With the present invention, on the surface of the substrate described inthe foregoing (Substrate Structure), that is, the substrate with theinternal fuel flow part provided therein, at least the face thereof, incontact with the cells, and interconnectors, being the insulator, thereare formed a plurality of cells each comprising a fuel electrode, anelectrolyte, and an air electrode, stacked in sequence (that is, eachcell comprised of the fuel electrode, electrolyte, and air electrode,stacked in that order). There are described in sequence hereinafterexamples of configuration of cells disposed on a substrate face.

Example 1 of Configuration of Cells Disposed on a Substrate Face

A plurality of cells each comprising a fuel electrode, an electrolyte,and an air electrode, stacked in sequence, are formed on a substratewith an internal fuel flow part provided therein, at least a facethereof, in contact with the cells, and interconnectors, being aninsulator. With the invention, respective cell areas may be the samealong the direction of fuel flow as shown in FIGS. 1(a) to 1(c), or maybe varied along the direction of the fuel flow as shown hereunder (referto Example 2 of Configuration of Cells Disposed on a Substrate Face). Inthis connection, a cell area generally refers to an effective powergeneration area of a cell, and since the effective power generation areaof the air electrode, or the effective power generation area of the fuelelectrode whichever is smaller is rate-limiting, the cell area refers tothe smaller one of those effective power generation areas.

Example 2 of Configuration of Cells Disposed on a Substrate Face

Configuration whereby respective cell areas are varied along thedirection of fuel flow has been developed by the inventor, et al., andby sequentially increasing respective cell areas along the direction ofthe fuel flow, it is possible to sequentially decrease current density,thereby enhancing power generation efficiency. Further, since there isan increase in the number of electrical connections in series, voltageincreases, and conversion efficiency of conversion from direct current(DC) to alternating current (AC) can be enhanced.

FIGS. 6(a) to 6(c) are views showing the configuration according toExample 2. FIG. 6(a) is a perspective view, FIG. 6(b) a plan view, andFIG. 6(c) a sectional view taken on line A-A in FIG. 6(b), showing theconfiguration expanded so as to be larger than that in FIG. 6(b). Asshown in FIGS. 6(a) to 6(c), on either the upper side face or theunderside face, or both the faces of a porous insulator substrate 21 ina shape hollow-flat, in cross-section, with an internal fuel flow part27 provided therein, a least the face thereof, in contact withrespective cells 22, and interconnectors 26, being an insulator, thereare formed in series a plurality of the cells 22 each made up of a fuelelectrode 23, an electrolyte 24, and an air electrode 25, stacked insequence, and the cells 22 adjacent to each other are connected throughthe intermediary of the respective interconnectors 26.

In FIG. 6(c), the interconnector 26 is seen covering part of the surfaceof the air electrode 25, however, may cover the entire surface thereof.Further, in FIG. 6(c), blank portions indicated by S may be filled upwith an interconnector material. In those respects described, the sameapplies to Working Examples that will be described hereinafter.

Then, the configuration whereby the respective cell areas are variedalong the direction of the fuel flow is adopted. In FIGS. 6(a) to 6(c),there is shown the case of the respective cell areas being sequentiallyincreased along the direction of the fuel flow, as indicated by an arrow(→Z), illustrating a mode for varying the respective cell areas. Morespecifically, as indicated by 25′, 25′, 25′″ in FIG. 6(c), therespective cells are structured such that the areas of the fuelelectrode 23, and the areas of the electrolyte 24 are sequentiallyincreased along the direction of the fuel flow, followed by sequentialincrease in the area of the air electrode 25. Further, FIGS. 6(a) to6(c) show the case of the substrate being in a shape hollow-flat orrectangular in cross-section, however, the same applies to the cases ofthe substrate being in shapes other than that in cross-section, such aspolygonal, elliptical, and so forth, in cross-section.

Besides the above, as other modes for varying the respective cell areasalong the direction of the fuel flow, the respective cells may bestructured as described under items (1) to (3) given hereunder:

(1) One cell group is made up of a plurality of the cells identical incell area. The SOFC module is structured such that there aresequentially disposed the cell groups with the respective cells thereof,sequentially increasing in cell area along the direction of the fuelflow. For example, there are disposed the respective cell groups insequential order, such as the cell group a→the cell group b→the cellgroup c . . . along the direction of the fuel flow, in which case, thecell areas of the respective cells of the cell group b are larger thanthose of the cell group a, the cell areas of the respective cells of thecell group c are larger than those of the cell group b, and so on.

(2) One cell group is made up of a plurality of the cells identical incell area. The SOFC module is structured such that there aresequentially, and alternately disposed the cell groups, and the cellsnot belonging to any of the cell groups (that is, individual cells)along the direction of the fuel flow while the cell areas of therespective cells are sequentially increased. For example, there aredisposed the respective cell groups and the individual cells in amanner, such as the cell group a→the cell b→the cell group c→the cell d. . . along the direction of the fuel flow, in which case, the cell areaof the cell b is larger than the cell areas of the respective cells ofthe cell group a, the cell areas of the respective cells of the cellgroup c are larger than the cell area of the cell b, and so on.

(3) One cell group is made up of a plurality of the cells identical incell area. The SOFC module is structured such that there are disposedthe cell groups, and the cells not belonging to any of the cell groups(that is, individual cells) sequentially along the direction of the fuelflow, but at random, while the cell areas of the respective cells aresequentially increased along the direction of the fuel flow. Forexample, the respective cell groups, and the individual cells aredisposed in a manner, such as the cell group a→the cell b→the cell c→thecell group d→the cell e . . . along the direction of the fuel flow, inwhich case, the cell area of the cell b is larger than the cell areas ofthe respective cells of the cell group a, the cell area of the cell c isrendered larger than that of the cell b, the cell areas of therespective cells of the cell grouped are larger than that of the cell c,and so on.

Electric power is drawn out between the cell at the forefront in thedirection of the fuel flow, and the cell at the rearmost in thedirection of the fuel flow. As fuel is consumed at the respective cells,the fuel becomes gradually thinner along the direction of the fuel flow,however, in the case of Example 2 shown in FIGS. 6(a) to 6(c), the cellareas of the respective cells are sequentially increased, so thatcurrent density sequentially decreases. In this respect, the sameapplies to the cases of other modes described under items (1) to (3) asabove. Accordingly, power generation efficiency can be enhanced.Further, since there is an increase in the number of the cells, of whichadjacent cells are electrically connected in series, voltage increases,and conversion efficiency of conversion from direct current (DC) toalternating current (AC) can be enhanced.

Example 3 of Configuration of Cells Disposed on a Substrate Face

FIGS. 7(a) to 7(c) are views showing Example 3 of Configuration of CellsDisposed on a Substrate Face, as the target for the manufacturing methodaccording to the invention. FIG. 7(a) is an oblique perspective view,FIG. 7(b) a plan view, and FIG. 7(c) a sectional view taken on line A-Ain FIG. 7(b), showing the SOFC module expanded so as to be larger thanthat in FIG. 7(b). As shown in FIGS. 7(a) to 7(c), in each of aplurality of rows from first to n-th rows, on either the upper side faceor the underside face, or both the faces of an insulator substrate 21 ina shape rectangular or hollow-flat, in cross-section, there are formed aplurality of cells 22 each made up of a fuel electrode 23, anelectrolyte 24, and an air electrode 25, stacked in sequence, and theadjacent cells 22 are electrically connected in series with each otherthrough the intermediary of the respective interconnectors 26. In FIGS.7(a) to 7(c), there is shown the case of two rows of the first andsecond rows, however, the same applies to the case of three or morerows. In FIG. 7(a), there is shown the direction of current flow betweenthe cells on the top face (surface) of the SOFC module, however, thedirection of current flow between the cells disposed on the undersideface (rear face) of the SOFC module is the same.

Further, respective cell areas may be the same along the direction offuel flow as shown in FIG. 1, however, the respective cell areas may bevaried along the direction of the fuel flow as shown in FIGS. 6(a) to(c). In FIGS. 7(a) to 7(c), there is shown the case where the respectivecells areas are sequentially increased along the direction of the fuelflow, as indicated by an arrow (→Z).

Besides the above, the respective cells may be structured as describedunder items (1) to (3) given hereunder, as with the previously describedcase (Example 2 of Configuration of Cells Disposed on a Substrate Face),on the basis of a sub-module unit in the respective rows:

(1) One cell group is made up of a plurality of the cells identical incell area. The SOFC module is structured such that there aresequentially disposed the cell groups with the respective cells thereof,sequentially increasing in cell area along the direction of the fuelflow.

(2) One cell group is made up of a plurality of the cells identical incell area. The SOFC module is structured such that there aresequentially, and alternately disposed the cell groups, and the cellsnot belonging to any of the cell groups (that is, individual cells)along the direction of the fuel flow while the cell areas of therespective cells are sequentially increased.

(3) One cell group is made up of a plurality of the cells identical incell area. The SOFC module is structured such that there are disposedthe cell groups, and the cells not belonging to any of the cell groups(that is, individual cells) sequentially along the direction of the fuelflow, but at random, while the cell areas of the respective cells aresequentially increased along the direction of the fuel flow.

Further, the SOFC module may be structured such that cell areas of therespective cells disposed in the respective rows are varied along thedirection of the fuel flow on a row-to-row basis, so as to be variedbetween the sub-module units. FIGS. 8(a), 8(b), and FIGS. 9(a), 9(b) areviews showing several examples of such modes, respectively. In thosefigures, respective rows from first to fourth rows indicate respectivesub-SOFC modules, omitting description of the interconnectors. In thoseexamples, a plurality of the sub-modules are disposed such that facesthereof, with the cells disposed thereon, are in parallel with eachother, and in those figures, to show a mode of cell lineup, there areshown the faces thereof, on the side of the cell lineup. Fuel is insequentially fed from the sub-module in the forefront row to thesub-module in the row adjacent thereto, and inside the sub-modules inthe respective rows in FIGS. 8(a), 8(b), and FIGS. 9(a), 9(b),respectively, the fuel flows from the lower part to the upper part. InFIGS. 8(a), 8(b), and FIGS. 9(a), 9(b), reference numeral 28 denotes afuel flow path through which the fuel is sequentially fed to therespective adjacent SOFC sub-modules. Further, those figures show thecase of the SOFC module having four rows, however, the same applies tothe case of the SOFC module having two to three rows, or five or morerows.

The example shown in FIG. 8(a) represents the case where the cell areasof the respective cells are sequentially increased on the basis of thesub-module unit. In FIG. 8(a), the SOFC module is structured such thatthe cells areas of the respective cells 29 in the first row are small,the cell areas of the respective cells 29 in the second row, on theright side of the first row, are larger than those in the first row, thecell areas of the respective cells 29 in the third row, on the rightside of the second row, are larger than those in the second row, and thecell areas of the respective cells 29 in the fourth row, at theright-hand end, are larger than those in the third row.

The example shown in FIG. 8(b) represents the case where the cell areasof respective cells are varied within a group of the cells, on arow-to-row basis, that is, within the sub-module unit, and further, thecell areas of respective cells are varied by the sub-module. In FIG.8(b), the SOFC module is structured such that the respective cell areasof six cells 29 (a group of six cells identical in cell area), on thelower end sides of both the first row at the leftmost end, and thesecond row next to the first row, are smaller while the cell areas offive cells 29 (a group of five cells identical in cell area) positionedabove the six cells 29 are larger than those of the six cells 29. Withrespect to the third row on the right side of the second row, four cells29 (a group of four cells identical in cell area) on the lower end sidethereof are structured so as to be smaller in cell area while five cells29 (a group of five cells identical in cell area) positioned above thefour cells 29 are structured so as to be larger in cell area than thefour cells 29. With respect to the fourth row at the rightmost end, fivecells 29 (a group of five cells identical in cell area) on the lower endside thereof are structured so as to be smaller in cell area while threecells 29 (a group of three cells identical in cell area) positionedabove the five cells 29 are structured so as to be larger in cell areathan the five cells 29.

With the example shown in FIG. 9(a), respective cells 29 in respectiverows from the first row at the leftmost end to the third row arestructured so as to be identical in cell area while respective cells 29in the fourth row are structured so as to be larger in cell area thanthe cells 29 in the respective rows from the first row to the third row.With the example shown in FIG. 9(b), respective cells 29 in respectiverows from the first row at the leftmost end to the third row arestructured so as to identical in cell area, and with respect torespective cells 29 in the fourth row at the rightmost end, six cells 29(a group of six cells identical in cell area) on the lower end sidethereof are structured so as to be smaller in cell area while five cells29 (a group of five cells identical in cell area) positioned above thesix cells 29 are structured so as to be larger in cell area than the sixcells 29.

In the cases of the examples of modes shown in FIGS. 8(a), 8(b), andFIGS. 9(a), 9(b), respectively, electric power is drawn out between thecell of the first row, at the forefront in the direction of the fuelflow, and the cell of the fourth row, at the rearmost in the directionof the fuel flow. The fuel is consumed at the respective cells tothereby become gradually thinner along the direction of the fuel flow,however, since the respective cells or the respective air electrodesthereof are varied in cell area along the direction of the fuel flow ona cell group unit basis, or a sub-module unit basis, the same effect asthat in the case of Example 2 of Configuration of Cells Disposed on aSubstrate Face, as described hereinbefore, can be obtained. In addition,since the plurality of the cells are formed in each of the plurality ofthe rows from the first row to the n-th row, so as to be electricallyconnected in series, a multitude of the cells can be lined up.Accordingly, large electric power can be obtained with a compactstructure.

Process of Fabricating the SOFC Module By the Manufacturing MethodAccording to the Invention

When fabricating the SOFC module according to the manufacturing methodof the invention, on the surface of the substrate with the internal fuelflow part provided therein, at least the face thereof, in contact withthe cells, and interconnectors, being the insulator, there are formed aplurality of cells each comprising a fuel electrode, an electrolyte, andan air electrode, stacked in sequence. In that case, prior to theformation of the air electrode on the respective electrolytes, theco-sintered body is formed as previously described under FundamentalFeatures of the Invention (1) to (6).

Construction for Configuration of Interconnector Between Adjacent Cells

With the SOFC module structured as described in the foregoing, theinterconnector is disposed between the adjacent cells. With the presentinvention, by use of a dense material, as the constituent material ofthe interconnector, in portions of the respective interconnectors, wheregas-sealing performance is required, such as the portions thereof,between respective electrolytic films of the adjacent cells, and soforth, a coarse material can be used between the air electrode and thedense material. The interconnector is a conductor linking between theadjacent cells, that is, linking the air electrode of the precedingcell, with the fuel electrode of the immediately following cell, and canbe structured in the shape of a sheet, wire, or in other appropriateshapes.

Herein, in the description of the present invention, the term “dense” inthe dense material described as above means a state having densitycorresponding to not less than 90%, preferably not less than 95% of thetheoretical density of the material. In contrast, in the description ofthe present invention, the term “coarse” in the coarse materialdescribed as above means a state having density in a range of from 20%to less than 90% against the theoretical density of the material. Withthe present invention, it is essential to use the dense material, as theconstituent material of the interconnector, at least between therespective electrolytic films of the adjacent cells, and on thatpremise, the dense material may be used in place of the coarse materialat spots where the coarse material is used as described hereinafter.

If the constituent material of the interconnector is, for example, (La,Sr) CrO₃, this material has poor sinterability, so that it is extremelydifficult to implement fabrication of the interconnector out of thesame, rendering it difficult to ensure gas-sealing performance.Accordingly, with the present invention, by use of the denseinterconnector material, or the interconnector material turning dense bysintering, as the constituent material of the interconnector between theadjacent cells, at least in portions of the interconnector, coming intocontact with the fuel electrode and the electrolyte, the denseinterconnector is formed. As a result, gas-sealing performance isenhanced, thereby preventing gas from leaking between theinterconnector, and the respective electrolytes. In addition, with theuse of the dense material, electrical contact can be secured. Further,as described above, the coarse material can be used between therespective air electrodes and the dense material. By so doing, it ispossible to obtain an advantageous effect that the fabrication of theinterconnectors can be implemented concurrently with the formation ofthe air electrodes, or at a temperature lower than the sinteringtemperature for the air electrodes.

There are described in sequence hereinafter configuration constructionsof the interconnectors between the respective cells adjacent to eachother in the SOFC module fabricated according to the manufacturingmethod of the invention, and a process of fabricating theinterconnectors (including the process for forming co-sintered bodyprior to the formation of air electrode on the electrolyte). FIG. 10 isa view showing an interconnector configuration construction and a basicof fabricating the same. In FIGS. 10 to 20, the under side views arethose for enlarging a part of the upper side views. In FIGS. 10 to 20, areference numeral 30 is a substrate, 31 a fuel electrode, 32 anelectrolyte (film), 33 air electrode, and the air electrode 33 isdisposed on the top face of the electrolyte film 32.

Interconnector Configuration Construction 1

FIG. 10 is a view showing an interconnector configuration construction1. The underside face of the interconnector [in FIG. 10, a portionthereof, indicated as “interconnector (need not be dense)”] is normallyin contact with the upper face of the electrolyte, however, there can bethe case where spacing exists therebetween. FIG. 10 shows the case wherethe spacing exists therebetween, as indicated by S in the figure. Inthis respect, the same applies to FIGS. 11 to 15, and FIGS. 17 to 20,referred to hereinafter.

A dense interconnector is disposed between the adjacent cells (therespective cells disposed side by side in FIG. 10, the same applies toFIGS. 11 to 20, referred to hereinafter). With the presentinterconnector configuration construction 1, the dense material is usedin portions of the respective interconnectors, coming into contact withthe fuel electrode and the electrolyte, where gas-sealing performance isrequired, while the coarse material is used between the respective airelectrodes and the dense material. In the case of material composedmainly of an oxide expressed by, for example, chemical formula (Ln, M)CrO₃ (in the chemical formula, Ln refers to lanthanoids, and M refers toBa, Ca, Mg, or Sr), this material has poor sinterability, so that it isextremely difficult to implement fabrication of the interconnector outof the same. Accordingly, as with the present interconnectorconfiguration construction 1, by use of the dense material in theportions of the respective interconnectors, coming into contact with thefuel electrode and the electrolyte, where gas-sealing performance isrequired, gas-sealing performance can be enhanced, and gas can beprevented from leaking between the respective interconnectors, and theelectrolytes. In addition, with the use of the dense material,electrical contact can be secured.

In general, the interconnector is linked with the respective fuelelectrodes by disposing the interconnector underneath the respectivefuel electrodes [refer to FIGS. 1(c), 6(c) and 7(c)]. In contrast, withthe present configuration construction 1, by causing the denseinterconnector material to be present on the upper faces of therespective fuel electrodes, as shown in FIG. 10, the fabrication can befacilitated. Further, as there is adopted the construction wherein partsof the respective electrolytes are covered by the interconnector,gas-sealing performance can be enhanced. In respect of the use of thecoarse material between the respective air electrodes, and the densematerial, the same applies to configuration constructions 2 to 11 thatwill be described hereinafter.

Now, on the premise that the dense interconnector material is disposedat specific spots as dscribed above, the dense material may be usedinstead of the coarse material at spots where the coarse material isnormally used. For example, in the case of using a mixture of glass andAg (Ag serving as an electroconductive material) as the interconnectormaterial, selection can be made as appropriate among (1) use of themixture in the portions of the interconnectors [the portions thereof,indicated as “interconnector (need not be dense)” in FIG. 10], and useof the dense interconnector material other than the former, in theportions of the interconnectors, indicated as [“interconnector (dense)”in FIG. 10], (2) use of a dense mixture selected from the mixture, inthe portions of the interconnectors, indicated as [“interconnector(dense)” in FIG. 10], and use of an interconnector material other thanthe former, in the portions of the interconnectors [the portionsthereof, indicated as “interconnector (need not be dense)” in FIG. 10],(3) use of a dense mixture selected from the mixture, in both theportions of the interconnectors, indicated as [“interconnector (dense)”and the portions of the interconnectors [the portions thereof, indicatedas “interconnector (need not be dense)”, in FIG. 10], (4) use of a densemixture selected from the mixture, in the portions of theinterconnectors, indicated as [“interconnector (dense)” in FIG. 10], anduse of a coarse mixture selected from the mixture, in the portions ofthe interconnectors [the portions thereof, indicated as “interconnector(need not be dense)”, in FIG. 10], and so forth. In this respect, thesame applies to Interconnector Configuration Construction 2 to 11,referred to hereinafter.

Fabrication of Interconnector Configuration Construction 1

A process of fabricating the interconnector configuration construction 1is basically a process for co-sintering the respective fuel electrodes,the respective electrolytes, and the dense interconnector material, orthe interconnector material turning dense by sintering, andsubsequently, attaching the respective air electrodes thereto. In such acase, attachment of the interconnector material is carried out after theelectrolyte is applied to the respective fuel electrodes. A co-sinteredbody of the fuel electrodes, and the electrolytes may be separatelyjoined to the substrate through the intermediary of the jointingmaterial, and so forth, however, the co-sintered body thereof may beseparately joined to the substrate through the intermediary of ajointing material, and so forth, however, such co-sintering may beexecuted by co-sintering of those including the substrate. The processcomprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) Portions of the respective fuel electrodes, to which theinterconnector is to be attached, are masked in advance.

(3) Dipping with electrolyte is carried out. This step can beimplemented, for example, by dipping, in other words, immersing aworkpiece, having come through the steps (1) to (2) as above, intoelectrolytic slurry.

(4) The portions of the respective fuel electrodes are exposed byremoving a mask.

(5) The dense interconnector material, or the interconnector materialturning dense after co-sintering is subsequently attached so as to coverthe portions of the respective fuel electrodes as exposed, and portionsof the respective electrolytes [the portions of the interconnectors,indicated as “interconnector (dense)” in FIG. 10].

(6) The workpiece, having come through the steps (1) to (5) as above, issubjected to co-sintering. By so doing, the substrate, the fuelelectrodes and the interconnectors are co-sintered, thereby forming thedense interconnectors. In the case of using the interconnector materialturning dense after co-sintering, the dense interconnectors are formedafter this co-sintering. In this respect, the same applies to the caseof using the interconnector material turning dense after co-sinteringwith Interconnector Configuration Constructions as describedhereinafter.

(7) The air electrodes are applied, and sintered.

(8) The coarse interconnector is attached, corresponding to therespective portions of the interconnectors, that is, [the portionsthereof, indicated as “interconnector (need not be dense)”, in FIG. 10].The interconnector (need not be dense) is for linking the air electrodewith the dense interconnector.

Interconnector Configuration Construction 2

FIG. 11 is a view showing an interconnector configuration construction2. A dense interconnector is disposed between the adjacent cells. Withthe interconnector configuration construction 2, the dense material isdisposed on a part of the top face of the fuel electrode, and a portionof the dense material is linked with the coarse material. By so doing,there is made up a construction wherein the top of the dense materialexcept a coarse material portion of the interconnector is covered by theelectrolytes. As the interconnector configuration construction 2 has theconstruction wherein the top of the dense material is covered by theelectrolytes, gas-sealing performance can be further enhanced. In otherrespects, the structure of the interconnector configuration construction2 is the same as that for the interconnector configuration construction1.

Fabrication of Interconnector Configuration Construction 2

A process of fabricating the interconnector configuration construction 2is basically a process for co-sintering the respective fuel electrodes,the respective electrolytes, and the dense interconnector material, orthe interconnector material turning dense by sintering, andsubsequently, attaching the respective air electrodes thereto.Fabrication of the interconnector configuration construction 2 differsfrom fabrication of the interconnector configuration construction 1 inthat prior to applying the electrolyte to the respective fuel electrodesin such a case, attachment of the interconnector material is carriedout. A co-sintered body thereof may be separately joined to thesubstrate through the intermediary of a jointing material, and so forth,however, such co-sintering may be executed by co-sintering of thoseincluding the substrate. The process comprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) The dense interconnector material, or the interconnector materialturning dense after co-sintering is attached thereto. In order to attachthe interconnector (need not be dense) to the interconnector materiallater on, the surfaces of respective portions of the interconnectormaterial are masked

(3) Dipping with electrolyte is carried out. This step can beimplemented, for example, by dipping, in other words, immersing aworkpiece, having come through the steps (1) to (2) as above, into anelectrolytic slurry.

(4) A workpiece, having come through the steps (1) to (3) as above, issubjected to co-sintering. By so doing, the substrates, the fuelelectrodes and the dense interconnector material, or the interconnectormaterial turning dense after co-sintering are co-sintered. A mask may beremoved prior to co-sintering or need not be removed in the case ofusing a masking material that will be decomposed dense upon theco-sintering,

(5) The air electrodes are applied, and sintered.

(6) The coarse interconnector is attached to the respective portions ofthe cells, that is, [the portions thereof, indicated as “(need not bedense)”, in FIG. 11]. The interconnector (need not be dense) is forlinking the air electrode with the dense interconnector.

Interconnector Configuration Construction 3

FIG. 12 is a view showing an interconnector configuration construction3. The dense interconnector material is disposed between the adjacentcells. With the interconnector configuration construction 3, as shown inFIG. 12, the dense material is disposed between the top faces of therespective fuel electrodes, and an electrolyte film, and between theelectrolyte film continuous thereto and side faces of the respectivefuel electrodes (that is, the side faces thereof, on the upstream sideof the respective cells, in the direction of the fuel flow) continuousto the top face. By so doing, a contact area between the denseinterconnector material, and the respective electrolytes can beincreased, thereby enabling contact resistance between the denseinterconnector material, and the respective fuel electrodes to belowered. In other respects, the structure of the interconnectorconfiguration construction 3 is the same as that for the interconnectorconfiguration construction 2.

Fabrication of Interconnector Configuration Construction 3

A process of fabricating the interconnector configuration construction 3is basically a process for co-sintering the respective fuel electrodes,the respective electrolytes, and the dense interconnector material, orthe interconnector material turning dense by sintering, andsubsequently, attaching the respective air electrodes thereto.Fabrication of the interconnector configuration construction 3 is thesame as the fabrication of the interconnector configuration construction2, bur differs from the fabrication of the interconnector configurationconstruction 2 in that prior to applying the electrolyte to therespective fuel electrodes in such a case, the portions of theinterconnector material are masked. A co-sintered body thereof may beseparately joined to the substrate through the intermediary of ajointing material, and so forth, however, such co-sintering may beexecuted by co-sintering of those including the substrate. The processcomprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) The dense interconnector material, or the interconnector materialturning dense after co-sintering is attached thereto. Portions of theinterconnector material are masked. Masking portions are spots where thecoarse interconnector material is disposed in a step (6) describedhereunder, that is, the top face of part of the respective portions ofthe interconnectors, indicated as [“interconnector (dense)” in FIG. 12],and between portions indicated as the electrolytes, on the right andleft sides, respectively.

(3) Dipping with electrolyte is carried out. This step can beimplemented, for example, by dipping, in other words, immersing aworkpiece, having come through the steps (1) to (2) as above, into anelectrolytic slurry.

(4) A workpiece, having come through the steps (1) to (3) as above, issubjected to co-sintering. By so doing, the substrates, the fuelelectrodes, the electrolytes, and the dense interconnector material, orthe interconnector material turning dense after co-sintering areco-sintered.

(5) The air electrodes are applied, and sintered.

(6) The coarse interconnector is attached to the respective portions ofthe cells, that is, [the portions thereof, indicated as “(need not bedense)”, in FIG. 12]. The interconnector (need not be dense) is forlinking the air electrode with the dense interconnector.

Interconnectors Configuration Construction 4

FIG. 13 is a view showing the interconnector configuration construction4. The dense interconnector material is disposed between the adjacentcells. With the interconnector configuration construction 4, the denseinterconnector material is disposed on the top faces of respectiveelectrolytic films, adjacent to each other, and between the adjacentelectrolytic films, and on side faces of the respective fuel electrodes,continuous to the former. As shown in FIG. 13, the dense material is ina sectional shape resembling the letter T, and the underside face of thehead thereof is in contact with the respective electrolytes while oneside face of the leg thereof (that is, a side face of the fuelelectrode, on the upstream side of the respective cells, in thedirection of the fuel flow) is in contact with the electrolyte and thefuel electrode continuing thereto, and the other side face of the legthereof is in contact with the other electrolyte. By so doing, a contactarea between the dense interconnector material, and the electrolytes canbe increased, and contact resistance between the interconnector, and thefuel electrode can be lowered, thereby enabling sealing performance tobe enhanced. In other respects, the structure of the interconnectorconfiguration construction 4 is the same as that for the interconnectorconfiguration construction 1.

Fabrication of Interconnector Configuration Construction 4

A process of fabricating the interconnector configuration construction 4is basically a process for co-sintering the respective fuel electrodes,and the respective electrolytes, subsequently, attaching the denseinterconnector material, or the interconnector material turning dense bysintering, and thereafter, attaching the respective air electrodesthereto. In this case, portions of the respective electrolytes, wherethe dense interconnector material, or the interconnector materialturning dense by sintering is attached after co-sintering of therespective fuel electrodes, and the respective electrolytes, are etchedaway. A co-sintered body thereof may be separately joined to thesubstrate through the intermediary of a jointing material, and so forth,however, such co-sintering may be executed by co-sintering of thoseincluding the substrate. The process comprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) Dipping with electrolyte is carried out. This step can beimplemented, for example, by dipping, in other words, immersing aworkpiece, having come through the step (1) as above, into anelectrolytic slurry.

(3) The workpiece having come through the steps (1) to (2) as above, issubjected to co-sintering. By so doing, the substrates, the fuelelectrodes and the electrolytes are co-sintered.

(4) The portions of the respective electrolytes, where the denseinterconnector material, or the interconnector material turning dense bysintering is attached, are etched away Etching spots correspond to theportions of the respective interconnectors, indicated as“[interconnector (dense)]”, in FIG. 13.

(5) The dense interconnector material, or the interconnector materialturning dense by sintering is attached. Attaching spots are the etchingspots described above, corresponding to the portions of the respectiveinterconnectors, indicated as “[interconnector (dense)]”, in FIG. 13.

(6) The workpiece, having come through the step (5) as above, issubjected to firing (sintering). By so doing, the dense interconnectorsare formed. In the case of using the interconnector material turningdense after co-sintering, the dense interconnectors are formed afterthis co-sintering. In this respect, the same applies to the case ofusing the interconnector material turning dense after co-sintering withInterconnector Configuration Constructions as described hereinafter.

(7) The air electrodes are applied, and sintered.

(8) The coarse interconnector is attached to the respective portions ofthe cells, indicated as (need not be dense) in FIG. 13. The coarseinterconnector (need not be dense) is for linking the air electrode withthe respective dense interconnectors.

Interconnector Configuration Construction 5

FIG. 14 is a view showing the interconnector configuration construction5. The dense interconnector is disposed between the adjacent cells. Withthe interconnector configuration construction 5, the denseinterconnector material is structured so as to continue from the topface of the electrolyte of the preceding cell of the adjacent cells to aside face of the electrolyte, coming into contact with the top face ofthe substrate, and to subsequently come into contact with a side face ofthe fuel electrode of the immediately following cell before furthercontinuing to the top face thereof. As a result, the respectiveelectrolytes can be more completely separated from each other incomparison with the case of the interconnector configurationconstruction 4. That is, the respective electrolytes of the adjacentcells are separated from each other. With the interconnectorconfiguration construction 5, gas leakage from the substrate can besealed with the dense interconnector material.

Fabrication of Interconnector Configuration Construction 5

A process of fabricating the interconnector configuration construction 5is basically a process for co-sintering the respective fuel electrodes,and the respective electrolytes, subsequently, etching away portions ofthe respective electrolytes, where the dense interconnector material, orthe interconnector material turning dense by sintering, disposing thedense interconnector material, or the interconnector material turningdense by sintering to be thereby sintered, and thereafter attaching therespective air electrodes thereto. A co-sintered body thereof may beseparately joined to the substrate through the intermediary of ajointing material, and so forth, however, such co-sintering may beexecuted by co-sintering of those including the substrate. The processcomprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) Dipping with electrolyte is carried out. This step can beimplemented, for example, by dipping, in other words, immersing aworkpiece, having come through the step (1) as above, into anelectrolytic slurry.

(3) The workpiece having come through the steps (1) to (2) as above, issubjected to co-sintering. By so doing, the substrates, the fuelelectrodes and the electrolytes are co-sintered.

(4) The portions of the respective electrolytes, where the denseinterconnector material, or the interconnector material turning dense bysintering is attached, are etched away. Etching spots correspond to theportions of the respective interconnectors, indicated as“[interconnector (dense)]”, in FIG. 14.

(5) The dense interconnector material, or the interconnector materialturning dense by sintering is attached.

(6) The air electrodes are applied thereto to be thereby sintered.

(7) The coarse interconnector is attached to the respective portions ofthe cells, indicated as (need not be dense) in FIG. 14. The coarseinterconnector (need not be dense) is for linking the air electrode withthe respective dense interconnectors

Interconnector Configuration Construction 6

FIG. 15 is a view showing the interconnector configuration construction6. The dense interconnector is disposed between the adjacent cells. Withthe interconnector configuration construction 6, the denseinterconnector material is structured so as to continue from the topface of the electrolyte of the preceding cell of the adjacent cells to aside face thereof, coming in contact with the top face of the substrate,and to come into contact with a side face of the fuel electrode of theimmediately following cell before continuing to between the top face ofthe fuel electrode and the underside face of the electrolyte. As aresult, the respective electrolytes of the adjacent cells are separatedfrom each other as with the case of the interconnector configurationconstruction 5. With the interconnector configuration construction 6,sealing performance against gas leakage even from a porous substrate canbe enhanced with the dense interconnector material.

Fabrication of Interconnector Configuration Construction 6

A process of fabricating the interconnector configuration construction 6is basically a process for co-sintering the respective fuel electrodes,the respective electrolytes, and the dense interconnector material, orthe interconnector material turning dense by sintering, subsequently,attaching the air electrodes thereto, and linking the denseinterconnector with the respective air electrodes. A co-sintered bodythereof may be separately joined to the substrate through theintermediary of a jointing material, and so forth, however, suchco-sintering may be executed by co-sintering of those including thesubstrate. The process comprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) The electrolytes formed in a sheet shape, and the denseinterconnector material, or the interconnector material turning dense bysintering, formed in a sheet shape, are alternately disposed so as topartially overlap each other. Overlapping portions each correspond to aspot on the top face of the fuel electrode of the following cell of theadjacent cells in FIG. 15.

(3) A workpiece having come through the steps (1) to (2) as above issubjected to co-sintering. By so doing, the fuel electrodes, theelectrolytes, and the dense interconnector material, or theinterconnector material turning dense by sintering are co-sintered.

(4) The air electrodes are applied thereto to be thereby sintered.

(5) The coarse interconnector is attached to the respective portions ofthe cells, indicated as (need not be dense) in FIG. 15. The coarseinterconnector (need not be dense) is for linking the air electrode withthe respective dense interconnectors

Interconnector Configuration Construction 7

FIG. 16 is a view showing the interconnector configuration construction7. The dense interconnector is disposed between the adjacent cells. Withthe interconnector configuration construction 7, the electrolytes of therespective cells are disposed so as to cover the fuel electrodeincluding a side face thereof. With the interconnector configurationconstruction 7, the dense interconnector material is structured so as tocontinue from a side face of the air electrode of the preceding cell ofthe adjacent cells to the top face of the electrolyte, coming in contactwith a side face thereof, and to subsequently come into contact with thetop face of the substrate, further continuing to between the undersideface of the electrolyte of the immediately following cell, and thesubstrate before further extended between the substrate and the fuelelectrode. As a result, the respective electrolytes of the adjacentcells are separated from each other. With the interconnectorconfiguration construction 7, sealing performance against gas leakageeven from a porous substrate can be enhanced with the denseinterconnector material. In the case where the dense interconnectormaterial is composed of, for example, an Ag-containing material, therecan be times when Ag is scattered if Ag is in single substance form.Accordingly, with the interconnector configuration construction 7, thetop of the Ag-containing material is covered with a glass material, andso forth, as shown in FIG. 16, thereby preventing scattering of Ag.

Fabrication of Interconnector Configuration Construction 7

A process of fabricating the interconnector configuration construction 7is basically a process for co-sintering the substrate, the respectivefuel electrodes, and the respective electrolytes, subsequently, etchingaway portions of the respective electrolytes, and portions of therespective fuel electrodes, to which the dense interconnector material,or the interconnector material turning dense by sintering is applied,disposing the dense interconnector material, or the interconnectormaterial turning dense by sintering to be thereby sintered, andthereafter attaching the respective air electrodes thereto. The processcomprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) Dipping with electrolyte is carried out. This step can beimplemented, for example, by dipping, in other words, immersing aworkpiece, having come through the step (1) as above, into anelectrolytic slurry.

(3) A workpiece having come through the steps (1) to (2) as above, issubjected to co-sintering. By so doing, the substrates, the fuelelectrodes and the electrolytes are co-sintered.

(4) The portions to which the dense interconnector material, or theinterconnector material turning dense by sintering is attached, areetched away. Etching spots correspond to portions indicated as theinterconnectors (dense: for example, containing Ag), in FIG. 16, thatis, portions each extending from a side face of the air electrode of thepreceding cell of the adjacent cells to the top face, and a side face ofthe electrolyte, and the top face of the substrate, up to between theunderside face of the electrolyte of the immediately following cell, andthe substrate

(5) The dense interconnector material, or the interconnector materialturning dense by sintering is attached. The reason why the denseinterconnector material is permeated up to the respective fuelelectrodes, as shown in FIG. 16, for example, as Ag-permeated portions,is that elements, for example, Ag undergo natural permeation

(6) The air electrodes are applied thereto to be thereby sintered.

(7) The top of the Ag-containing material as formed is covered with aglass material, and so forth, in the case of using an Ag-containingmaterial for the dense interconnector material, thereby preventingscattering of Ag. Parts indicated as “Ag-containing material etc.” inFIG. 16 correspond thereto.

Interconnector Configuration Construction 8

FIG. 17 is a view showing the interconnector configuration construction8. The dense interconnector is disposed between the adjacent cells. Asshown in a sectional view of FIG. 17, with the interconnectorconfiguration construction 8, respective cells are structured as seen insection such that a side face of the both side faces of the fuelelectrode, on the upstream side of fuel flow, is not covered with theelectrolyte while the other side face of the fuel electrode, on thedownstream side of the fuel flow, is covered with the electrolyte, andthe electrolyte further covers the top face of the substrate. Further,the dense interconnector is structured so as to continue from theelectrolyte on the top face of the substrate (between the electrolyteand the top face of the substrate), coming in contact with the top faceof the substrate to a side face of the fuel electrode of the immediatelyfollowing cell before coming into contact with the top face of theelectrolyte. As a result, the respective electrolytes of the adjacentcells are separated from each other. With the interconnectorconfiguration construction 8, the electrolytes are completely separatedfrom each other, that is, the respective electrolytes of the adjacentcells are separated from each other, and by disposing the denseinterconnector on the top face of the electrolyte, on the side of thecell, adjacent to the fuel electrode with which the dense comes intocontact, sealing performance can be enhanced. Further, since theelectrolyte covers between the side face of the fuel electrode, on thedownstream side of the fuel flow, and the top face of the substrate,sealing performance can be enhanced.

Fabrication of Interconnector Configuration Construction 8

A process of fabricating the interconnector configuration construction 8is basically a process for co-sintering the substrate, the respectivefuel electrodes, the dense interconnector material, or theinterconnector material turning dense by sintering, and the respectiveelectrolytes before attaching the respective air electrodes thereto. Theprocess comprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) The dense interconnector material, or the interconnector materialturning dense by sintering, formed in a sheet shape, is attached.Attaching spots correspond to portions indicated as the interconnector(dense) in FIG. 17.

(3) The electrolytes formed in a sheet shape are disposed. In this case,in relation to the fuel electrodes, the electrolytes formed in a sheetshape are disposed between the top face of the fuel electrodes, and theunderside of dense interconnector material, or the interconnectormaterial turning dense by sintering.

(4) A workpiece having come through the steps (1) to (3) as above issubjected to co-sintering. By so doing, the substrate, the fuelelectrodes, the dense interconnector material, or the interconnectormaterial turning dense by sintering, and the electrolytes, areco-sintered.

(5) The air electrodes are applied thereto to be thereby sintered.

(6) The coarse interconnector is attached to the respective portions ofthe cells, indicated as the interconnector (need not be dense) in FIG.17. The interconnector (need not be dense) is for linking the airelectrode with the respective dense interconnectors.

Interconnectors Configuration Construction 9

FIG. 18 is a view showing the interconnector configuration construction9. The dense interconnector is disposed between the adjacent cells. Asshown in FIG. 18, with the interconnector configuration construction 9,the respective cells are structured as seen in section such that a sideface of the both side faces of the fuel electrode, on the upstream sideof fuel flow, is not covered with the electrolyte while the other sideface of the fuel electrode, on the downstream side of the fuel flow, iscovered with the electrolyte, and the electrolyte covers the top face ofpart of the substrate. Further, the dense interconnector is structuredso as to continue from the electrolyte on the top face of the part ofthe substrate (between the top face of the substrate and theelectrolyte), coming into contact with the top face of the substrate,and further continuing to a side face of the fuel electrode of theimmediately following cell before coming into contact with the undersideface of the electrolyte (that is, between the underside face of theelectrolyte and the fuel electrode). As a result, the respectiveelectrolytes of the adjacent cells are separated from each other. Withthe interconnector configuration construction 9, the electrolytes arecompletely separated between the respective cells, that is, therespective electrolytes of the adjacent cells are completely separatedfrom each other. Thus, by disposing the dense interconnector so as tocontinue from the electrolyte on the top face of the part of thesubstrate (between the top face of the substrate and the electrolyte),coming into contact with the top face of the substrate, and furthercontinuing to the side face of the fuel electrode of the immediatelyfollowing cell before coming into contact with the underside face of theelectrolyte (that is, between the underside face of the electrolyte andthe fuel electrode), as described above, sealing performance can beenhanced.

Fabrication of Interconnector Configuration Construction 9

A process of fabricating the interconnector configuration construction 9is basically a process for co-sintering the respective fuel electrodes,the dense interconnector material, or the interconnector materialturning dense by sintering, and the respective electrolytes beforeattaching the respective air electrodes thereto. A co-sintered bodythereof may be separately joined to the substrate through theintermediary of a jointing material, and so forth, however, suchco-sintering may be executed by co-sintering of those including thesubstrate. The process comprises the following steps.

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) The dense interconnector material, or the interconnector materialturning dense by sintering is attached. Attaching spots correspond toportions indicated as the interconnector (dense) in FIG. 18.

(3) Dipping with electrolyte is carried out. This step can beimplemented, for example, by dipping, in other words, immersing aworkpiece, having come through the steps (1) to (2) as above, into anelectrolytic slurry.

(4) The workpiece having come through the steps (1) to (3) as above issubjected to co-sintering. By so doing, the substrate, the fuelelectrodes, the dense interconnector material, or the interconnectormaterial turning dense by sintering, and the electrolytes, areco-sintered.

(5) Portions of the electrolyte, on top of the dense interconnectormaterial, are removed by etching. The portions of the electrolyte, to beremoved, are portions on the right and left sides, respectively, of thebottom of a leg part (on the right side) of a portion of the cell,indicated as the interconnector (need not be dense) in FIG. 18, and FIG.18 shows the shape of the electrolyte after partial removal [theinterconnector (need not be dense) is not formed as yet at this stage].

(6) The air electrodes are applied thereto to be thereby sintered.

(7) The interconnector (need not be dense) is attached to respectiveportions of the cells, indicated as the interconnector “(need not bedense)”, in FIG. 18. In the case of using material containing metal,such as Ag, and so forth, as an interconnector (dense) material, therebyposing a problem with chemical stability of Ag and so forth, at theoperating temperature of an SOFC, such a problem can be avoided bycovering the interconnector (dense) material portions of the cells witha glass material, and so forth.

Interconnector Configuration Construction 10

FIG. 19 is a view showing the interconnector configuration construction10. The dense interconnector is disposed between the adjacent cells. Asshown FIG. 19, with the interconnector configuration construction 10,the respective cells are structured as seen in section such that a sideface of the both side faces of the fuel electrode, on the upstream sideof fuel flow, is not covered with the electrolyte while the other sideface of the fuel electrode, on the downstream side of the fuel flow, iscovered with the electrolyte, and the electrolyte covers the top face ofpart of the substrate. Further, the dense interconnector is structuredso as to continue from the top face of part of the electrolyte, on thetop face of the part of the substrate, to a side face thereof, cominginto contact with the top face of the substrate, and further continuingto a side face of the fuel electrode of the immediately following cellbefore coming into contact with the underside face of the electrolyte(that is, between the underside face of the electrolyte and the fuelelectrode). With the interconnector configuration construction 10, theelectrolytes are completely separated between the respective cells, thatis, the respective electrolytes of the adjacent cells are completelyseparated from each other. Thus, sealing performance can be enhanced bydisposing the dense interconnector so as to continue from the top faceof the part of the electrolyte, on the top face of the part of thesubstrate, coming into contact with the top face of the substrate, viathe side face of the part of the electrolyte, and further continuing tothe side face of the fuel electrode of the immediately following cellbefore coming into contact with the underside face of the electrolyte(that is, between the underside face of the electrolyte and the fuelelectrode), as described above.

Fabrication of Interconnector Configuration Construction 10

A process of fabricating the interconnector configuration construction10 is basically a process for co-sintering the respective fuelelectrodes, the dense interconnector material, or the interconnectormaterial turning dense by sintering, and the respective electrolytesbefore attaching the respective air electrodes thereto. A co-sinteredbody thereof may be separately joined to the substrate through theintermediary of a jointing material, and so forth, however, suchco-sintering may be executed by co-sintering of those including thesubstrate. The process comprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) The electrolytes formed in a sheet shape are placed on top of thefuel electrodes as shown as the electrolytes in FIG. 19.

(3) The dense interconnector material, or the interconnector materialturning dense by sintering, formed in a sheet shape, is disposed so asto cover the top face of part of the electrolyte, and a side facethereof while the other end of the dense interconnector material, or theinterconnector material turning dense by sintering comes underneath theelectrolyte (that is, between the fuel electrode and the electrolyte.The dense interconnector material, or the interconnector materialturning dense by sintering, as formed, is a sectional shape indicated asthe interconnector (dense) in FIG. 19, covering the top face of part ofthe electrolyte (extending to the top face of the substrate) on thedownstream side, in the direction of fuel flow, continuing to a sideface thereof, coming into contact with the top face of the substrate,and further continuing from a side face of the fuel electrode to the topface thereof as the respective cells are seen in section.

(4) A workpiece having come through the steps (1) to (3) as above issubjected to co-sintering. By so doing, the substrate, the fuelelectrodes, the dense interconnector material, or the interconnectormaterial turning dense by sintering, and the electrolytes, areco-sintered.

(5) The air electrodes are applied thereto to be thereby sintered.

(6) The interconnector (need not be dense) is attached. By so doing, theair electrode is linked with the respective dense interconnectors.

Interconnector Configuration Construction 11

FIG. 20 is a view showing the interconnector configuration construction11. As shown in FIG. 20, with the interconnector configurationconstruction 11, the respective cells are structured as seen in sectionsuch that a side face of the both side faces of the fuel electrode, onthe upstream side of fuel flow, is not covered with the electrolytewhile the other side face of the fuel electrode, on the downstream sideof the fuel flow, is covered with the electrolyte, and the electrolytecovers the top face of part of the substrate. Further, the denseinterconnector is structured so as to continue from the top face of partof the electrolyte, on the top face of the part of the substrate, to aside face of the fuel electrode of the immediately following cell, aftercoming into contact with a side face of the part of the electrolyte, andthe top face of the substrate, and further, to continue to a side faceof the electrolyte before coming into contact with the top face thereof.With the interconnector configuration construction 11, the electrolytesare completely separated between the respective cells, that is, therespective electrolytes of the adjacent cells are completely separatedfrom each other. Thus, sealing performance can be enhanced by disposingthe dense interconnector so as to continue from the top face of the partof the electrolyte, on the top face of the part of the insulatorsubstrate, to the side face of the fuel electrode of the immediatelyfollowing cell, after coming into contact with a side face of the partof the electrolyte, and the top face of the substrate and further, tocontinue to a side face of the electrolyte before coming into contactwith the top face thereof, as described above.

Fabrication of Interconnector Configuration Construction 11

A process of fabricating the interconnector configuration construction11 is basically a process for co-sintering the respective fuelelectrodes, the dense interconnector material, or the interconnectormaterial turning dense by sintering, and the respective electrolytesbefore attaching the respective air electrodes thereto. A co-sinteredbody thereof may be separately joined to the substrate through theintermediary of a jointing material, and so forth, however, suchco-sintering may be executed by co-sintering of those including thesubstrate. The process comprises the following steps:

(1) The fuel electrodes are disposed on the substrate. This step can beimplemented, for example, by applying powdery constituent material ofthe fuel electrode, in slurry form, to the substrate.

(2) The electrolytes formed in a sheet shape are placed on top of thefuel electrodes as shown as the electrolytes in FIG. 20.

(3) The dense interconnector material, or the interconnector materialturning dense by sintering, formed in a sheet shape, is disposed. Thedense interconnector material, or the interconnector material turningdense by sintering, as formed, is a sectional shape covering the topface of part of the electrolyte (extending to the top face of thesubstrate) on the downstream side of the respective cells, in thedirection of fuel flow, continuing to a side face of the electrolyte,and coming into contact with the top face of the substrate, and furthercontinuing from a side face of the fuel electrode to the top face of theelectrolyte after a side face thereof. The dense interconnectormaterial, or the interconnector material turning dense by sintering,formed in the sheet shape, are placed as indicated as the interconnector(dense) in FIG. 20,

(4) A workpiece having come through the steps (1) to (3) as above issubjected to co-sintering. By so doing, the substrate, the fuelelectrodes, the dense interconnector material, or the interconnectormaterial turning dense by sintering, and the electrolytes, areco-sintered.

(5) The air electrodes are applied thereto to be thereby sintered.

(6) The interconnector (need not be dense) is attached. By so doing, theair electrode is linked with the respective dense interconnectors.

With respective processes of fabricating the interconnectorconfiguration constructions 1 to 11, the constituent material of the airelectrode is disposed on the electrolytes prior to sintering.Temperature for the sintering varies depending on the constituentmaterial of the air electrode, and is normally in a range of 800 to1150° C. Further, the interconnector (need not be dense) is attachedbetween the dense interconnector and the respective air electrodes, andupon attachment thereof, heat treatment is applied as necessary. Heatingtemperature at that time varies depending on the kind of the constituentmaterial of the interconnector (need not be dense), and the constituentmaterials, and so forth of the air electrode, and the denseinterconnector, respectively, but the heat treatment can be appliednormally in a range of 200 to 800° C. In the case of using, for example,an Ag paste, heat treatment may be applied, but is not necessarilyrequired.

WORKING EXAMPLES

The invention is described in more detail hereinafter with reference toworking examples, however, it is to be understood that obviously theinvention is not limited thereto.

Working Example 1

Working Example 1 represents the case where the dense interconnector isattached in advance. FIG. 21 is a view broadly showing a method ofmanufacturing an SOFC module, and for clarity in explanation, the figureshows the case of the SOFC module provided with three cells. FIG. 22(a)is a perspective view of a substrate, FIG. 22(b) is a perspective viewof the substrate with the cells formed thereon, showing the substrate inFIG. 22(a) after enlarged and partially cut, and FIG. 22(c) is apartially sectional view of the SOFC module wherein the cells adjacentto each other are electrically connected in series through theintermediary of an interconnector.

Brief Explanation of a Manufacturing Method according to Working Example1

An SOFC module is manufactured by taking process steps (1) to (7) insequence, as shown in FIG. 21. In the process step (1), fuel electrodesare formed on a substrate by screen printing. In the process step (2),an interconnector material is provided on the respective fuel electrodesby screen printing. Subsequently, portions of the respectiveinterconnector materials are masked in the process step (3) to befollowed by dip coating with electrolytic material in the process step(4). In the process step (5), respective masks formed in the processstep (3) are removed, and thereafter, the substrate, the fuelelectrodes, the interconnector material, and electrolytes areco-sintered, thereby forming dense interconnectors. Subsequently, in theprocess step (6), air electrodes are screen printed on a co-sinteredbody to be thereby sintered. Then, in the process step (7), the denseinterconnector is linked with the respective air electrodes through theintermediary of an electroconductive paste.

1. Fabrication of a Substrate

(i) To mixed powders composed of nickel monoxide (manufactured by NipponChemical Industry Co. Ltd.), and an yttria stabilized zirconia(manufactured by Toso Co. Ltd.) mixed at a ratio of 1:4 by weight,addition of graphite (manufactured by Showa Denko Co. Ltd.) in 15 wt. %against the total quantity of the mixed powders was made, and distilledwater was added thereto before mixed in a ball mill for 20 hours. (ii)An organic solvent (mixed solvent of toluene and 2-propanol),dispersant, and antifoamer were added to a mixed solution under (i) asabove to be reduced into powders by use of a spray dryer. A porousinsulator substrate hollow flat in sectional shape was fabricated by thehydrostatic pressure pressing method using the powders as obtained. FIG.22(a) is the oblique perspective view of the substrate fabricated asabove.

2. Fabrication of Fuel Electrodes on the Porous Insulator SubstrateHollow Flat in Sectional Shape

(i) Slurry was prepared by adding an organic solvent (mixed solvent oftoluene and 2-propanol), dispersant, and antifoamer to 100 g of mixedpowders composed of nickel monoxide (manufactured by Nippon ChemicalIndustry Co. Ltd.), and an yttria stabilized zirconia (manufactured byToso Co. Ltd.) mixed at a ratio of 2:3 by weight before mixed in a ballmill for 20 hours. (ii) Fuel electrodes were formed by screen printingon the porous insulator substrate hollow flat in sectional shape,fabricated under (1, Fabrication of a substrate) as above. That is theprocess step (1) as shown in FIG. 21.

3. Application of an Interconnector Material

(i) Slurry was prepared by adding an organic solvent (mixed solvent oftoluene and 2-propanol), dispersant, and antifoamer to powders of La(Ti_(0.8) Nb_(0.2)) O₃ before mixed in a ball mill for 20 hours. (ii)The slurry obtained under (i) as above was applied to the fuelelectrodes by screen printing. Those are the process steps (1) to (2),as shown in FIG. 21.

4. Preparation of Electrolytic Material: Fabrication of Electrolytes onthe Porous Insulator Substrate Hollow Flat in Sectional Shape, andFabrication of Interconnectors

(i) Slurry was prepared by adding an organic solvent (mixed solvent oftoluene and 2-propanol), dispersant, and antifoamer to an yttriastabilized zirconia (manufactured by Toso Co. Ltd.) before mixed in aball mill for 24 hours. (ii) Masking was provided on a portion of theinterconnector material, smaller in width by 1 mm than the respectiveinterconnector materials applied under (3. Application of anInterconnector Material) as above, and a workpiece was immersed, thatis, dipped in the slurry obtained under (i) as above, which was repeatedtwice. Those are the process steps (2) to (4) via (3), as shown in FIG.21. (iii) The substrate processed under (ii) as above was subjected toheat treatment at 1500° C. for 7.5 hours, thereby co-sintering thesubstrate, the fuel electrodes, and electrolytes while forming denseinterconnectors. Those are the process steps (4) to (5), as shown inFIG. 21.

5. Fabrication of Air Electrodes

(i) Slurry was prepared by adding an organic solvent (mixed solvent oftoluene and 2-propanol), dispersant, and antifoamer to powders of aperovskite type oxide (La_(0.6)Sr_(0.4)) Co_(0.2)Fe_(0.8)O₃ before mixedin a ball mill for 20 hours. (ii) The slurry obtained under (i) as abovewas applied to the porous insulator substrate hollow flat in sectionalshape, fabricated under (1, Fabrication of a substrate) as above byscreen printing. (iii) The substrate processed under (ii) as above wassubjected to heat treatment at 1150° C. for 5 hours, thereby forming airelectrodes. Those are the process steps (5) to (6), as shown in FIG. 21.

6. Connection Between the Air Electrodes and Dense Interconnectors,Respectively

Ag paste was applied between the dense interconnector formed under (4.Fabrication of Interconnectors) as above, and the respective airelectrodes formed under (5, Fabrication of Air Electrodes) as above,thereby implementing connection therebetween. Those are the processsteps (6) to (7), as shown in FIG. 21.

Thus, there was manufactured an SOFC module comprising 32 cells whereinthe cells (each cell area=about 4.5 cm²) adjacent to each other areelectrically connected in series through the intermediary of theinterconnectors. FIG. 22(c) shows the SOFC module in partial section.The SOFC module manufactured was found satisfactorily sealed, and powergeneration tests to repeat start-up, operation, and shutdown wereconducted thereon, whereupon electric power of about 16 W at about 18Vwas obtained.

Working Example 2

Working Example 2 represents the case where the dense interconnector isattached subsequently. FIG. 23 is a view broadly showing a method ofmanufacturing an SOFC module, and for clarity in explanation, the figureshows the case of the SOFC module provided with three cells.

Brief Explnation of a Manufacturing Method According to Working Example2

An SOFC module is manufactured by taking process steps (1) to (7) insequence, as shown in FIG. 23. In the process step (1), fuel electrodesare formed on a substrate by screen printing. In the process step (2),portions of the respective fuel electrodes are masked, and subsequently,a work piece is subjected to dip coating with an electrolytic materialin the process step (3). Thereafter, in the process step (4), afterremoving masks formed in the process step (2), the substrate, the fuelelectrodes, electrolytes are co-sintered. In the process step (5) aninterconnector material in a tape-like form is stuck onto an exposedpotion of the fuel electrode so as to slightly overlap the respectiveelectrolytes. In the process step (6), air electrodes are screen printedon the workpiece and are subjected to heat treatment. By so doing, theair electrodes are fired, and at the same time, dense interconnectorsare formed. Then, in the process step (7), the dense interconnector islinked with the respective air electrodes through the intermediary of anelectroconductive paste.

1. Fabrication of a Substrate

(i) To mixed powders composed of nickel monoxide (NiO: manufactured byNippon Chemical Industry Co. Ltd.), and an yttria stabilized zirconia(manufactured by Toso Co. Ltd.) mixed at a ratio of 1:4 by weight,addition of graphite (manufactured by Showa Denko Co. Ltd.) in 15 wt. %against the total quantity of the mixed powders was made, and distilledwater was added thereto before mixed in a ball mill for 20 hours. (ii)An organic solvent (mixed solvent of toluene and 2-propanol),dispersant, and antifoamer were added to a mixed solution under (i) asabove to be reduced into powders by use of a spray dryer. A porousinsulator substrate hollow flat in sectional shape [about 6 cm (W)×about2.5 cm (H)×about 25 cm (L)] was fabricated by the extrusion moldingmethod using the powders as obtained.

2. Fabrication of Fuel Electrodes on the Porous Insulator SubstrateHollow Flat in Sectional Shape

(i) Slurry was prepared by adding an organic solvent (mixed solvent oftoluene and 2-propanol), dispersant, and antifoamer to 100 g of mixedpowders composed of nickel monoxide (NiO: manufactured by NipponChemical Industry Co. Ltd.), and an yttria stabilized zirconia(manufactured by Toso Co. Ltd.) mixed at a ratio of 2:3 by weight beforemixed in a ball mill for 20 hours. (ii) Fuel electrodes were formed byscreen printing on the porous insulator substrate hollow flat insectional shape, fabricated under (1, Fabrication of a substrate) asabove. That is the process step (1) as shown in FIG. 23.

3. Fabrication of Electrolytes

(i) Slurry was prepared by adding an organic solvent (mixed solvent oftoluene and 2-propanol), dispersant, and antifoamer to an yttriastabilized zirconia (manufactured by Toso Co. Ltd.) before mixed in aball mill for 24 hours. (ii) A masking tape was attached tointerconnector-forming parts of the porous insulator substrate hollowflat in sectional shape, fabricated under (2. Fabrication of FuelElectrodes on the Porous Insulator Substrate Hollow Flat in SectionalShape) as above, and a workpiece obtained was immersed, that is, dippedin the slurry obtained under (i) as above, which was repeated twice.Those are the process steps (1) to (3), as shown in FIG. 23. Thereafter,the masking tape was removed. (iii) The substrate processed under (ii)as above was subjected to heat treatment at 1500° C. for 7.5 hours,thereby co-sintering the substrate, the fuel electrodes, andelectrolytes. Those are the process steps (3) to (4), as shown in FIG.23.

4. Attachment of Interconnector Material

(i) Slurry was prepared by mixing an organic solvent (mixed solvent oftoluene and 2-propanol) with a mixture of Ag powders (produced byIshifuku Kinzoku Kogyo Co. Ltd.) and glass powders (SiO₂—SrO—K₂O—Na₂Obase bonding material, trade name: ASF 700 produced by Asahi Glass Co.Ltd.), mixed at a ratio of 6:4 by weight, in a ball mill for 20 hours.By the doctor blade method using the slurry, tape-like slurries wereformed. (ii) The tape-like slurry obtained under (i) as above was stuckto masking portions of the porous insulator substrate hollow flat insectional shape, fabricated under (3, Fabrication of Electrolytes)described as above, that is, the portions thereof, where the fuelelectrode is exposed after removal of the masking tape, so as to overlapthe respective electrolytes to the extent of about 1 mm. That is theprocess step (5), as shown in FIG. 23.

5. Fabrication of Air Electrodes and Densification of InterconnectorMaterial

(i) Slurry was prepared by adding an organic solvent (mixed solvent oftoluene and 2-propanol), dispersant, and antifoamer to powders of aperovskite type oxide (La_(0.6)Sr_(0.4)) Co_(0.2)Fe_(0.8)O₃ before mixedin a ball mill for 20 hours. (ii) The slurry obtained under (i) as abovewas applied to the porous insulator substrate hollow flat in sectionalshape, fabricated under (4, Attachment of Interconnector Material)described as above, and the surface of the electrolyte on the respectivefuel electrodes, by screen printing. (iii) The substrate processed under(ii) as above was subjected to heat treatment at 925° C. for 2 hours,thereby forming air electrodes as well as dense interconnectors. That isthe process step (6) shown in FIG. 23.

6. Formation of Material for Effecting Connection Between the AirElectrodes and the Dense Interconnectors, Respectively

Slurry was prepared by mixing an organic solvent (mixed solvent oftoluene and 2-propanol) with a mixture of Ag powders (produced byIshifuku Kinzoku Kogyo Co. Ltd.) and glass powders (SiO₂—SrO—K₂O—Na₂Obase bonding material, trade name: ASF 700 produced by Asahi Glass Co.Ltd.), mixed at a ratio of 8:2 by weight, in a ball mill for 20 hours.By the screen printing method using the slurry, tape-like slurries wereformed.

7. Connection Between the Air Electrodes and Dense Interconnectors,Respectively

The tape-like slurry obtained under (6. Formation of Material forEffecting Connection between the Air Electrodes and the DenseInterconnectors, respectively) described as above was disposed on thesurfaces of the respective air electrodes obtained under (5. Fabricationof Air Electrodes and Densification of Interconnector Material)described as above, and the dense interconnectors, and was subsequentlysubjected to heat treatment at 800° C. for 2 hours, thereby implementingconnection between the respective air electrodes, and the denseinterconnector. Those are the process steps (6) to (7), as shown in FIG.23.

Thus, there was manufactured an SOFC module comprising 32 cells whereinthe cells (each cell area=about 4.5 cm²) adjacent to each other areelectrically connected in series through the intermediary of theinterconnectors. The SOFC module manufactured was found satisfactorilysealed, and power generation tests to repeat start-up, operation, andshutdown were conducted thereon, whereupon electric power of about 20 Wat about 22V was obtained.

Working Example 3

Ag powders (produced by Kojundo Chemicals Co. Ltd.), and glass powders(SiO₂—Al₂O₃—K₂O base glass sealing material: softening point 800° C.)were mixed at various ratios ranging from a ratio of 9:1 to 3:7 byweight, and mixtures obtained were subjected to heat treatment atvarious temperatures, thereby fabricating an interconnector.Measurements were taken on gas-sealing performance andelectroconductivity of the interconnector for evaluation of the same asa constituent member of an SOFC module.

The results of the evaluation are shown in Table 1 below. As shown inTable 1, it is evident that if an electroconductive material is Ag, heattreatment temperature need to be below 950° C. in order to obtainacceptable gas-sealing performance (indicated as sealing performance inTable 1), and electroconductivity. It is also evident thatelectroconductivity is acceptable even if heat treatment temperature is800° C., however, this temperature pose a problem in respect of sealingperformance. Further, it is shown that electroconductivity is acceptableif Ag content is not lower than 30 wt. %. TABLE 1 Ag powder:glass heattreatment temperature (° C.) powder (wt. ratio) 800 900 925 950 1000 9:1sealing perform. X ◯ ◯ X X conductivity ◯ ◯ ◯ X X 8:2 sealing perform. X◯ ◯ X X conductivity ◯ ◯ ◯ X X 7:3 sealing perform. X ◯ ◯ X Xconductivity ◯ ◯ ◯ X X 6:4 sealing perform. X ◯ ◯ X X conductivity ◯ ◯ ◯X X 5:5 sealing perform. X ◯ ◯ X X conductivity ◯ ◯ ◯ X X 4:6 sealingperform. X ◯ ◯ X X conductivity ◯ ◯ ◯ X X 3:7 sealing perform. X ◯ ◯ X Xconductivity ◯ ◯ ◯ X X

1. A method of manufacturing a solid oxide fuel cell module comprising aplurality of cells each made up of a fuel electrode, an electrolyte, andan air electrode sequentially formed on a surface of a substrate with aninternal fuel flow part provided therein, at least a face of thesubstrate, in contact with the cells, and interconnectors, being aninsulator, and the cells adjacent to each other, being electricallyconnected in series through the intermediary of the respectiveinterconnectors, said method of manufacturing the solid oxide fuel cellmodule comprising the steps of: co-sintering the respective fuelelectrodes, and the respective electrolytes; subsequently forming adense interconnector out of a dense interconnector material, or aninterconnector material turning dense by sintering in at least parts ofthe solid oxide fuel cell module, in contact with the respective fuelelectrodes, and the respective electrolyte; and forming an air electrodeon the respective electrolytes before electrically connecting the airelectrode with the respective dense interconnectors.
 2. A method ofmanufacturing a solid oxide fuel cell module comprising a plurality ofcells each made up of a fuel electrode, an electrolyte, and an airelectrode sequentially formed on a surface of a substrate with aninternal fuel flow part provided therein, at least a face of thesubstrate, in contact with the cells, and interconnectors, being aninsulator, and the cells adjacent to each other, being electricallyconnected in series through the intermediary of the respectiveinterconnectors, said method of manufacturing the solid oxide fuel cellmodule comprising the steps of: co-sintering the substrate, therespective fuel electrodes, and the respective electrolytes;subsequently forming a dense interconnector out of a denseinterconnector material, or an interconnector material turning dense bysintering in at least parts of the solid oxide fuel cell module, incontact with the respective fuel electrodes, and the respectiveelectrolytes; and forming an air electrode on the respectiveelectrolytes before electrically connecting the air electrode with therespective dense interconnectors.
 3. A method of manufacturing a solidoxide fuel cell module comprising a plurality of cells each made up of afuel electrode, an electrolyte, and an air electrode sequentially formedon a surface of a substrate with an internal fuel flow part providedtherein, at least a face of the substrate, in contact with the cells,and interconnectors, being an insulator, and the cells adjacent to eachother, being electrically connected in series through the intermediaryof the respective interconnectors, said method of manufacturing thesolid oxide fuel cell module comprising the steps of: co-sintering therespective fuel electrodes, the respective electrolytes, and a denseinterconnector material, or an interconnector material turning dense byco-sintering, in at least parts of the solid oxide fuel cell module, incontact with the respective fuel electrodes, and the respectiveelectrolytes; and forming an air electrode on the respectiveelectrolytes before electrically connecting the air electrode with therespective dense interconnectors.
 4. A method of manufacturing a solidoxide fuel cell module comprising a plurality of cells each made up of afuel electrode, an electrolyte, and an air electrode sequentially formedon a surface of a substrate with an internal fuel flow part providedtherein, at least a face of the substrate, in contact with the cells,and interconnectors, being an insulator, and the cells adjacent to eachother, being electrically connected in series through the intermediaryof the respective interconnectors, said method of manufacturing thesolid oxide fuel cell module comprising the steps of: co-sintering thesubstrate, the respective fuel electrodes, the respective electrolytes,and a dense interconnector material, or an interconnector materialturning dense by co-sintering, in at least parts of the solid oxide fuelcell module, in contact with the respective fuel electrodes, and therespective electrolytes: and forming an air electrode on the respectiveelectrolytes before electrically connecting the air electrode with therespective dense interconnectors.
 5. A method of manufacturing a solidoxide fuel cell module comprising a plurality of cells each made up of afuel electrode, an electrolyte, and an air electrode sequentially formedon a surface of a substrate with an internal fuel flow part providedtherein, at least a face of the substrate, in contact with the cells,and interconnectors, being an insulator, and the cells adjacent to eachother, being electrically connected in series through the intermediaryof the respective interconnectors, said method of manufacturing thesolid oxide fuel cell module comprising the steps of: disposing a denseinterconnector material, or an interconnector material turning dense byco-sintering, in portions of the respective fuel electrodes;subsequently covering the respective fuel electrodes, and the denseinterconnector material, or the interconnector material turning dense byco-sintering before co-sintering the respective fuel electrodes, thedense interconnector material, or the interconnector material turningdense by co-sintering, and the respective electrolytes, thereby formingdense interconnectors; forming an air electrode on the respectiveelectrolytes; and subsequently electrically connecting the air electrodewith the respective dense interconnectors.
 6. A method of manufacturinga solid oxide fuel cell module comprising a plurality of cells each madeup of a fuel electrode, an electrolyte, and an air electrodesequentially formed on a surface of a substrate with an internal fuelflow part provided therein, at least a face of the substrate, in contactwith the cells, and interconnectors, being an insulator, and the cellsadjacent to each other, being electrically connected in series throughthe intermediary of the respective interconnectors, said method ofmanufacturing the solid oxide fuel cell module comprising the steps of:disposing a dense interconnector material, or an interconnector materialturning dense by co-sintering, in portions of the respective fuelelectrodes; subsequently covering the respective fuel electrodes, andthe dense interconnector material, or the interconnector materialturning dense by co-sintering before co-sintering the substrate, therespective fuel electrodes, the dense interconnector material, or theinterconnector material turning dense by co-sintering, and therespective electrolytes, thereby forming dense interconnectors; formingan air electrode on the respective electrolytes; and subsequentlyelectrically connecting the air electrode with the respective denseinterconnectors.
 7. A method of manufacturing a solid oxide fuel cellmodule according to claim 1, wherein a mixture of MgO, and MgAl₂O₄ isused as a constituent material of the substrate with the internal fuelflow part provided therein, at least a face of the substrate, in contactwith the cells, and the interconnectors, being the insulator.
 8. Amethod of manufacturing a solid oxide fuel cell module according toclaim 7, wherein the mixture of MgO, and MgAl₂O₄ is a mixture of MgO,and MgAl₂O₄, containing 20 to 70 vol. % of MgO.
 9. A method ofmanufacturing a solid oxide fuel cell module according to claim 1,wherein an yttria stabilized zirconia expressed by chemical formula(Y₂O₃)_(x)(ZrO₂)_(1-x) (in the chemical formula, x=0.03 to 0.12) is usedas a constituent material of the substrate with the internal fuel flowpart provided therein, at least a face of the substrate, in contact withthe cells, and the interconnectors, being the insulator.
 10. A method ofmanufacturing a solid oxide fuel cell module according to claim 1,wherein a mixture of a mixture composed of MgO, and MgAl₂O₄, and anyttria stabilized zirconia expressed by chemical formula(Y₂O₃)_(x)(ZrO₂)_(1-x) (in the chemical formula, x=0.03 to 0.12) is usedas a constituent material of the substrate with the internal fuel flowpart provided therein, at least a face of the substrate, in contact withthe cells, and the interconnectors, being the insulator.
 11. A method ofmanufacturing a solid oxide fuel cell module according to claim 10,wherein the mixture of MgO, and MgAl₂O₄ is a mixture of MgO, andMgAl₂O₄, containing 20 to 70 vol. % of MgO.
 12. A method ofmanufacturing a solid oxide fuel cell module according to claim 1,wherein a constituent material of the substrate with the internal fuelflow part provided therein, at least a face of the substrate, in contactwith the cells, and the interconnectors, being the insulator, ismaterial composed of Ni diffused in a range not more than 35 vol. %. 13.A method of manufacturing a solid oxide fuel cell module according toclaim 1, wherein material composed mainly of Ni, is used as aconstitutent material of the fuel electrode.
 14. A method ofmanufacturing a solid oxide fuel cell module according to claim 1,wherein a mixture of Ni and an yttria stabilized zirconia expressed bychemical formula (Y₂O₃)_(x)(ZrO₂)_(1-x) (in the chemical formula, x=0.03to 0.12), with not less than 40 vol. % of Ni diffused in the mixture, isused as a constituent material of the fuel electrode.
 15. A method ofmanufacturing a solid oxide fuel cell module according to claim 1,wherein, an yttria stabilized zirconia expressed by chemical formula(Y₂O₃)_(x)(ZrO₂)_(1-x) (in the chemical formula, x=0.05 to 0.15) is usedas a constituent material of the electrolyte.
 16. A method ofmanufacturing a solid oxide fuel cell module according to claim 1,wherein a scandia stabilized zirconia expressed by chemical formula(Sc₂O₃)_(x)(ZrO₂)_(1-x) (in the chemical formula, x=0.05 to 0.15) isused as a constituent material of the electrolyte.
 17. A method ofmanufacturing a solid oxide fuel cell module according to claim 1,wherein an yttria doped ceria expressed by chemical formula(Y₂O₃)_(x)(CeO₂)_(1-x) (in the chemical formula, x=0.02 to 0.4) is usedas a constituent material of the electrolyte.
 18. A method ofmanufacturing a solid oxide fuel cell module according to claim 1,wherein a gadolinia doped ceria expressed by chemical formula(Gd₂O₃)_(x)(CeO₂)_(1-x) (in the chemical formula, x=0.02 to 0.4) is usedas a constituent material of the electrolyte.
 19. A method ofmanufacturing a solid oxide fuel cell module according to claim 1,wherein material composed of a mixture of a glass and anelectroconductive material is used as a constituent material of theinterconnector.
 20. A method of manufacturing a solid oxide fuel cellmodule according to claim 19, wherein the glass in the mixture of theglass and the electroconductive material is a glass with thermalexpansion coefficient falling in a range of 8.0 to 14.0×10⁻⁶K⁻¹.
 21. Amethod of manufacturing a solid oxide fuel cell module according toclaim 19, wherein the glass in the mixture of the glass and theelectroconductive material is a glass with a softening point falling ina range of 600 to 1000° C.
 22. A method of manufacturing a solid oxidefuel cell module according to claim 19, wherein the electroconductivematerial in the mixture of the glass and the electroconductive materialis a metal.
 23. A method of manufacturing a solid oxide fuel cell moduleaccording to claim 22, wherein the metal is at least one kind of metalselected from the group consisting of Pt, Ag, Au, Ni, Co, W, and Pd. 24.A method of manufacturing a solid oxide fuel cell module according toclaim 22, wherein the metal is an alloy containing Ag.
 25. A method ofmanufacturing a solid oxide fuel cell module according to claim 19,wherein the electroconductive material in the mixture of the glass andthe electroconductive material is an electroconductive oxide.
 26. Amethod of manufacturing a solid oxide fuel cell module according toclaim 25, wherein the electroconductive oxide is a perovskite typeceramics composed of not less than two elements selected from the groupconsisting of La, Cr, Y, Ce, Ca, Sr, Mg, Ba, Ni, Fe, Co, Mn, Ti, Nd, Pb,Bi, and Cu.
 27. A method of manufacturing a solid oxide fuel cell moduleaccording to claim 25, wherein the electroconductive oxide is an oxideexpressed by chemical formula (Ln, M)CrO₃ (in the chemical formula, Lnrefers to lanthanoids, and M refers to Ba, Ca, Mg, or Sr).
 28. A methodof manufacturing a solid oxide fuel cell module according to claim 25,wherein the electroconductive oxide is an oxide expressed by chemicalformula M(Ti_(1-x) Nb_(x))O₃ (in the chemical formula, M refers to atleast one element selected from the group consisting of Ba, Ca, Li, Pb,Bi, Cu, Sr, La, Mg, and Ce, x=0 to 0.4).
 29. A method of manufacturing asolid oxide fuel cell module according to claim 19, whereinelectroconductive material content of the mixture of the glass and theelectroconductive material is not less than 30 vol. % of the mixture.30. A method of manufacturing a solid oxide fuel cell module accordingto claim 19, wherein the mixture of the glass and the electroconductivematerial is subjected to heat treatment at not higher than the meltingpoint of the electroconductive material after the mixture is appliedbetween the fuel electrode of one of the adjacent cells, and the airelectrode of the other cell.
 31. A method of manufacturing a solid oxidefuel cell module according to claim 1, wherein only portions of theinterconnector connecting the fuel electrode of one of the adjacentcells with the air electrode of the other cell, in contact with the fuelelectrode, and the electrolyte, respectively, are formed of materialcomposed mainly of Ag.
 32. A method of manufacturing a solid oxide fuelcell module according to claim 1, wherein only portions of theinterconnector connecting the fuel electrode of one of the adjacentcells with the air electrode of the other cell, in contact with the fuelelectrode, and the electrolyte, respectively, are formed of materialcomposed of one kind or not less than two kinds of material selectedfrom the group consisting of Ag, Ag solder, and a mixture of Ag and theglass.
 33. A method of manufacturing a solid oxide fuel cell moduleaccording to claim 1, wherein only portions of the interconnectorconnecting the fuel electrode of one of the adjacent cells with the airelectrode of the other cell, in contact with the fuel electrode, and theelectrolyte, respectively, are formed of an electroconductive oxide. 34.A method of manufacturing a solid oxide fuel cell module according toclaim 1, wherein an oxide material containing Ti is used as aconstituent material of the interconnector connecting the fuel electrodeof one of the adjacent cells with the air electrode of the other cell.35. A method of manufacturing a solid oxide fuel cell module accordingto claim 34, wherein the oxide material containing Ti is materialexpressed by chemical formula M(Ti_(1-x) Nb_(x))O₃ (in the chemicalformula, M refers to at least one element selected from the groupconsisting of Ba, Ca, Pb, Bi, Cu, Sr, La, Li, and Ce, x=0 to 0.4).